Talk:Number needed to treat

Reversion of Psarka's Reversion
Listen up Psarka; I have no doubts you have heard these words before, but I will say them anyways. In this instance at least, you are arrogant and lack both manners and the expertise sufficient to say what you have.

Your nearly 900 word post here is a testament to just how extreme your need to criticize my work is. Instead of spending such an absurd amount of time on explaining why you will revert my edits, did you perhaps think you might instead spend such time on simply making the edits you feel are appropriate? The only thing you have done here is waste your time to justify wasting mine, all while never improving the quality of this article. You seem to have been so incensed by my request not to delete my work without reason that you set out to prove my incompetence just to spite me for making such a bold request.

Sincerely, Lumentex

--Lumentex (talk) 04:28, 12 November 2018 (UTC)


 * I am sorry you feel this way. Do as you wish. Psarka (talk) 05:27, 12 November 2018 (UTC)

Reasons for reverting edits by Lumentex
Hi Lumentex,

I'm sorry, but I'm reverting your edits. Reading your message "Completely rewrote this section to correct many inaccuracies and greatly increased clarity of explanations. DO NOT REVERT WITHOUT THOROUGH EXPLANATION OF REASONING." I get the feeling that you are very emotional about your additions, but also that you had a hunch that they will get reverted. What made you think that? Did you saw some weakness in your text when you wrote it?

Or maybe you thought that inevitably some evil guy will show up to destroy your valuable effort? If so, I'm afraid that no matter what I write, you already made up your mind and will curse me to hell.

Well do that, while I will try to do my best explaining my point of view in the politest and most constructive way I can. Here I go.

First you did not correct many inaccuracies. If you read the old version of that section generously, you will see that all the numbers and notions are accurate. The text is quite poor, I agree, but accurate.

Second, your explanations made the 'Interpretation' column less tricky to understand, but are very verbose. I would like to try to find a middle ground between the two versions.

Your other additions are valuable, but they should find their place in different articles. Why? Take a look at the table at the bottom of the article. NNT is one epidemiological measure out of 25(!). All the discussion in this article should be focused on the NNT itself, and not the broad context of epidemiology.

When I think about the article such as NNT, I imagine a reader that wants to quickly become familiar with the terminology of epidemiology measurements. So they click around and try to understand the differences between the measurements and their usage. My goal is to provide them this understanding as painlessly as I can.

That includes not burdening their brain with extraneous information that they could easily find in a dedicated article. In particular:


 * Sentence "The treatment may be a drug in the form of a pill or injection, a surgical procedure, or many other possibilities" should find its place in Treatment and control groups or Clinical trial


 * Chunk of text "This is typically a type of study <...> but are much more difficult and time-consuming to perform" should find its place in Clinical trial


 * Chunk of text "The control group may receive a placebo <...> quality of the placebo" should find its place in Clinical trial or Clinical endpoint or Treatment and control groups

Repeating the same information again and again and again does not make things clear. It makes reader annoyed that they have to constantly skip over the same ramblings.

Finally, if you forgive me, your contribution is not of high quality. Consider the following things that caught my eye:


 * You write a sentence 'There are a number of factors that can affect the meaning of the NNT". What would you expect in a following sentence? I would expect an elaboration on these factors. Instead, you continue with "The treatment may be a drug in the form of a pill or injection, a surgical procedure". Why? How pill vs injection vs surgical procedure alter the meaning of NNT?


 * You write "The following examples", and follow up with "In this example".


 * Your text contains too much boilerplate such as "depending on the situation", "or many other possibilities", "The following examples", "In this example", "it is important to understand", "This is typically a type", "which may be a reduction or halt in worsening of the condition, an improvement in the condition, or an outright cure of the condition.".


 * You make strong claims without any citations, such as "This <...> type of study that would occur only if <...>", "Prospective studies produce much higher quality evidence <...>"


 * In fact, you did not add a single citation


 * You redefine $$I_e$$ and $$I_u$$ differently from how they were defined in the article introduction.


 * You write "$$I_e$$ is the probability <...> this is the inverse of the probability <...>". This is incorrect. Inverse of a probability is never a probability.


 * Sentence "For simplicity, a low number of participants will be used, thought scientific studies almost always require many more." just appears out of nowhere in the second row of the table.


 * You write "Notice that, even though the treatment was effective in eight of ten cases (only one less than the previous example)", but the previous example had two out of ten.


 * You write "This is because" and then give a definition of NNT. That's not helpful.

If you decide to give another shot to this section, go ahead. But don't feel obliged, there are plenty of articles that would benefit much more from your attention than this one. I made an effort to clean up epidemiology measurements corner of the wikipedia (see my notes here https://en.wikipedia.org/wiki/User:Psarka/What_a_mess!), but ran out of steam. One page that is a particularly in need of love is Population Impact Measures. If you could try to sort that one out, it would be wonderful.

Sincerely, Paulius Psarka (talk) 22:02, 11 November 2018 (UTC)

Random medical student
as a random medical student with no experience with editing or contributing to wikipedia...this article makes a very simple concept wildly confusing and doesn't "fit" with the other 99% of articles I see on here. I have no idea who the audience is supposed to be when writing on a topic like this, but seems like it needs to at least show the equation for people like myself that just want a quick refresh on NNT. — Preceding unsigned comment added by 208.79.8.122 (talk) 23:35, 11 September 2014 (UTC)


 * The equation is (and was for a long time now, I suppose) present. Psarka (talk) 22:26, 8 September 2018 (UTC)

OR and RR
I have problems with odds ratio and relative risks being munged as they presently are. Why not present the OR=1/6 and the RR=1/4 as different measures? Johannes Hüsing (talk) 09:34, 18 April 2008 (UTC)


 * They are no longer munged. Psarka (talk) 22:27, 8 September 2018 (UTC)

CER and EER
--Hey. I have no idea how to edit a table, but I think the worked example table could use a little   --clarification. If you agree, could you make the change? --CER 	control event rate 	= events / subjects in control group --EER 	experimental event rate = events / subjects in experimental group --"Events" should be stated as "events in control group" and "events in experimental group", --respectively. Using "events" alone makes it sound like it's using the total events between groups. —Preceding unsigned comment added by 76.69.33.145 (talk) 22:08, 4 February 2008 (UTC)


 * Just go to http://en.wikipedia.org/wiki/Template:ARR_RRR_worksheet and edit away... ;-) T.pienn (talk) 23:44, 19 January 2009 (UTC)


 * I suppose this was resolved some time ago. Psarka (talk) 22:31, 8 September 2018 (UTC)

Attributable risk in the table
---I changed attributable risk in the table to EER-CER (before it was listed as EE/[EE+CE] - EN/[EN+CN]). Anyway, I think it would be a good idea to get rid of attributable risk all together, since it is just a synonym for absolute risk increase. Anyone have any objections? Crackles (talk) 21:40, 24 May 2011 (UTC)


 * Attributable risk stuff is now fixed in accordance to the dictionary of epidemiology. Psarka (talk) 22:31, 8 September 2018 (UTC)

Take out an example
I took out this example:
 * the drug gabapentin, frequently used for neuropathic pain, only gives appreciable symptom relief in about 33% of all cases; the NNT is therefore 3.

I think we need to know how often the pain goes away without treatment before we can compute the NNT here. NNT always depends on quality of the drug and likelihood of the defined endpoint without the drug. For example, if 10% of patients get better by themselves, then the NNT would be slightly bigger than 4. AxelBoldt 22:43, 30 May 2005 (UTC)


 * I simply added a number from my own experience. I should have sourced it from the Bandolier pain site. The NNT is not affected by spontaneous improvement. JFW | T@lk  08:32, 31 May 2005 (UTC)


 * From reading the Bandolier article, I believe NNT is affected by spontaneous improvement; in fact their first migraine example explicitely compares a placebo control group's outcome with the treatment group's outcome. With treatment 5% recur, without treatment 30% recur, so the NNT is 1/(30%-5%)=4. AxelBoldt 19:58, 31 May 2005 (UTC)


 * Number needed to treat refers to the number of individuals that need to be treated to appreciate a beneficial result in addition to those in whom the result would be observed without the treatment. It is derived in studies which have endpoints, therefore the endpoint for the outcome is implicit.  The statement "drug x provides relief in only 33% of cases" isn't sufficient to determine a NNT.  You need data on how many subjects got relief without geting drug x.  See the difference between a case-control study and a cohort study.Bakerstmd 03:33, 25 May 2007 (UTC)


 * Shall we find a better example? It seems you're correct about the spontaneous recovery rate, but spontaneous recovery rate is subtracted from the response in the treatment group before calculating the NNT. JFW | T@lk  01:49, 2 Jun 2005 (UTC)


 * As I see, better example was found. Psarka (talk) 22:33, 8 September 2018 (UTC)

Statins
I disagree with the removal of the NNT data for statins. It is a concrete example written in plain English for non mathematicians and non science majors. If you have another contradictory value, add it and add the source. I am restoring the value. Business week, is a reliable source. I came to the article after reading the article and was surprised it wasn't mentioned. The example is written so that the average non scientific reader can understand the concept. --Richard Arthur Norton (1958- ) (talk) 11:40, 31 March 2008 (UTC)


 * As I indicated on your talk page, you are misrepresenting the source. People take statins for various indications, and you are not distinguishing between primary prevention sec, primary prevention in diabetics, and secondary prevention after numerous cardiovascular pathologies. I urge you to revise your contribution and discuss here first before reinserting this content again. JFW | T@lk  15:53, 31 March 2008 (UTC)


 * I think your confusing verifiability with truth. The number is verifiable from a reliable source, if you have information to modify it or disparage it, please fell free to add it. The encyclopedia is for everyone not just statisticians. You haven't presented any data that disparages the number used, and the source for the reference is given. ultimately its boils down to is Business Week a reliable source, and what evidence do have that disparages the number. You may notice that my information is sourced, the rest of the article except the lede is not sourced. No one is served by removing data from a reliable source. I suggest keeping the data, and you provide information disparaging the number, and they can exist side-by-side. I am not a clinician, I am a medicinal chemist and I found the BW explanation the best example in plain English. --Richard Arthur Norton (1958- ) (talk) 16:02, 31 March 2008 (UTC)

I wish you'd have the common courtesy to discuss before you revert! Your source is doubtful, but even so you are misrepresenting it. Your professional background has no bearing on this. JFW | T@lk  16:24, 31 March 2008 (UTC)


 * Neither might like what I have to say, but I am use to that, and perhaps you might find common ground using this as a start. First of all, the 1 or 2 sentences make for a great example in plain English - better even than the table, which of course is hardly surprising, as it the table more technical. Also, you will find it hard to find a technical paper that deals simply with the issue, as it a tool taken-as-granted. However, the context is terrible, specifically the conclusion that the NNT of 100 is not worthwhile (statins are harmless drugs, going generic too, so cheap) to save 1 person a heart attack - in fact the relative risk (3% / 2%) is a staggering 50% which is surely why they recommend 40m Americans should be on them. Furthermore the writer then immediately compares them to antibiotics for h-pylori, with a lower NNT, etc, and somehow cannot see the point - which is that very 1-in-a-100 person. But the reason is, of course, the journalist set out to write a "story", and so he adapted science to his end (consciously or not) - and an encypledia should not reference stories. Can I suggest instead that you simply adapt the text of that paragraph into the Wiki, and leave out the reference? The only other idea I can think of is that there are a number of on-line statistics book, and they may come close to what is needed as a replacement - but really it does not need a reference at all, it is fairly fundamental.....io_editor (talk) 17:19, 31 March 2008 (UTC)


 * In general, I have no problems with including information like this as a practical example. This issue is discussed frequently, with different drugs and different sources.  See this magazine article for another set of numbers.  However, rather than appearing like we're bashing statins to promote our point of view, I'd prefer to see this used as an opportunity to highlight some of the limitations of the NNT.  For example, every study will produce a different number (at least slightly); different statins have different NNTs; different groups have different NNTs; every endpoint has a different NNT; combinations of drugs have different NNTs.  The NNT for statins is different for a diabetic, a tobacco user, an obese man, a woman, etc.  Furthermore, the NNT for heart attacks prevented over three years is different for the NNT measured for deaths prevented over ten years.  There are a few scholarly papers addressing the issue, such as this one.


 * However, it might be simpler to switch to a different drug class: perhaps aspirin to prevent heart attacks, but perhaps osteoporosis would be better.  There are some recent Cochrane reviews  that we could use for reliable numbers.  Using osteoporosis treatments as our example appeals to me because the number of confounding factors is substantially lower compared to heart disease, and it gives us an opportunity to present the difference between "treating the lab report" and "treating the patient".  WhatamIdoing (talk) 17:30, 31 March 2008 (UTC)

If the purpose of this article is to help readers understand number needed to treat, why not avoid controversial examples entirely? Primary prevention numbers are often high, and tend to have wider variability between studies. Maybe we could choose a secondary prevention example that isn't as open to various interpretations (I like the previous suggestion from WhatamIdoing of ASA for Myocardial Infarction).Sisyphus (talk) 19:02, 31 March 2008 (UTC)


 * thought it would be nice to use the statin data as an example. I don't actually mind (I am not averse of statin-bashing when there is bashing to be done), but I object to the lack of clarity that flows from regurgitating the Business Week story without qualifiers. I have now rephrased the addition in a way that I think makes reasonable sense: the absolute risk of cardiac events in the ASCOT-LLA study was low, therefore to get them lower still with a small dose of atorvastatin was quite a feat.
 * My version avoids the classical "big pharma versus the public interest" cliché and obviously drives home the message that primary prevention with statins is always going to be an expensive business (see the bandolier summary, about as good science as you're ever going to get). Comments invited. JFW | T@lk  19:59, 31 March 2008 (UTC)


 * If the statin example remains controversial, I propose as a clear case of the use of NNTs to guide treatment decisions - a Cochrane Review about the use of antidepressants in the treatment of chronic pain. JFW |  T@lk  20:09, 31 March 2008 (UTC)


 * Marking this as resolved, as I see a nice Statins example in the text. Psarka (talk) 22:39, 8 September 2018 (UTC)

Business Week redux
I am adding back in the BW reference. It seems you prefer citing journals written by statisticians for other statisticians. The BW is the only RS definition written in plain English. This here is a great article if you already know the subject, BW is great for me, and I am a scientist. One more reference does no harm. --Richard Arthur Norton (1958- ) (talk) 20:26, 31 March 2008 (UTC)


 * I had the impression that my addition was reasonly plain English. If it is not, please change the phrasing to make it more understandable. I have preserved the source as a compromise, but I have removed the quote because it adds nothing to the summary already provided. I hope you can live with that. JFW | T@lk  21:11, 31 March 2008 (UTC)

You expressed NNT as a percentage, which did not seem correct, but I didn't change it for fear of having it reversed. I had already trimmed the quote to satisfy your objections. --Richard Arthur Norton (1958- ) (talk) 22:11, 31 March 2008 (UTC)


 * That was indeed a mistake, which has already corrected. I still find the quote terribly imprecise (it's not 3% vs 2%, those are rounded figures), and the article remains in my view a shabby source. It doesn't quote the name of the trial,  let alone provide a full reference, and it presumes that just because Pfizer paid for it, it was therefore "conducted by Pfizer" (which is incorrect and casts aspersions on the integrity of the researchers).
 * I did ask you directly to correct my version to make it sound more like plain English. I really don't understand why you prefer a quote in a footnote over an opportunity to make the Wikipedia content easier to understand. JFW | T@lk  07:49, 1 April 2008 (UTC)

I don't think the Business Week article serves as a reliable source for purposes of this article. However, I take the point from Richard's argument that the Business Week article explains NNT in a way that is more intelligible than most. So how about modeling the explanation here after that article? --Una Smith (talk) 15:34, 1 April 2008 (UTC)


 * I have no problem with the style used by BW, although I note again the several problems with the example chosen by the journalist. JFW | T@lk  15:48, 1 April 2008 (UTC)


 * There is no ruling from Arbcom on using quotes in footnotes. A Supreme Court agreeing to hear a case, that you have an opinion on, does not mean your opinion has been validated. It only means that Arbcom agreed to hear the opinions of the involved parties. Deleting the reference that you have already expressed a negative opinion on is premature. I know you don't like references from non medical journals, but this is an encyclopedia for everyone, not just people who have degrees in statistics. I have already agreed to move the information from the body to a footnote. --Richard Arthur Norton (1958- ) (talk) 02:45, 16 May 2008 (UTC)


 * The Arbcomm is not an arbiter on style; there is consensus against the use of quotes in the way that you insist on doing. My point in the edit summaries was that perhaps you should not be undoing my edits while being involved in that particular Arbcomm case. Until I saw that case I was unaware of the fact that you had been editing against consensus on WP:CITE all along. JFW | T@lk  17:19, 16 May 2008 (UTC)


 * Incidentally, I think the way the page deals with the example at present does not need "degrees in statistics" (you keep on using the same point, which I have addressed numerous times). If people are desperate for a plain-language summary written in newspaper style by a journalist busy trying to prove a point, they can click the URL to the Business Week article. Strictly speaking, the Bandolier source is relatively plain-language and is "fit for purpose" vis a vis the Business Week source. JFW | T@lk  17:22, 16 May 2008 (UTC)


 * Marking this as resolved, as I see a nice Statins example in the text. Psarka (talk) 22:40, 8 September 2018 (UTC)

Let reader choose examples
Although I understand the concept of NNT, this article still is rather opaque to me. Probably also to many other readers. So, how about making it more concrete for the reader by adding links to other Wikipedia articles on applications of NNT? Also edit those articles to include the NNT data. --Una Smith (talk) 05:07, 1 April 2008 (UTC)


 * This search shows a moderate-sized list of articles linking to NNT. Some of them might be appropriate, although the few I checked tend to mention it in passing, instead of explaining it.  WhatamIdoing (talk) 05:51, 1 April 2008 (UTC)


 * Good idea. Looking at those links, I find inconsistent usage:  NNT is expressed as "1/N" or as "N". --Una Smith (talk) 06:02, 1 April 2008 (UTC)


 * The article already gives examples. We'd be better off providing more examples rather than using other content elsewhere (which may change) to illustrate our points. NNT is a number larger than on 1 by definition, so 1/N probably refers to 1/ARR (absolute risk reduction). JFW | T@lk  07:49, 1 April 2008 (UTC)


 * Marking this as resolved, as article has plenty of examples, and there is no "N" anymore. Psarka (talk) 22:42, 8 September 2018 (UTC)

Definition
Above, JFW says "NNT is a number larger than on 1 by definition" but I don't see that in the article. On the contrary, the article Derivation section defines NNT as 1/(pB - pA) which looks like a number smaller than 1. And pB - pA in the Derivation is ARR in the Worked Example. It is possible for ARR to be greater than 1, in which case NNT would be smaller than 1. The Derivation is incomplete. Also, the Worked Example has an internal inconsistency: it states that OR is both 4 and 0.25. Finally, I find it more helpful to give a series of abstract equations first in full, then with numbers plugged in, rather than in a sketch parallel as in the table format. --Una Smith (talk) 15:49, 1 April 2008 (UTC)
 * The NNT is computed as 1/(pB – pA) which is in fact "a number larger than 1 by definition" - because pA and pB are probabilities measured not as percentages but as decimals (of one) - and 1/(decimal-of-one) is always "a number larger than 1 by definition". It is also not possible for ARR (this is not the relative risk, but the difference between those pair of decimals) to be greater than one. You are correct about the OR, it is confusing the way that it is both 4 and 0.25 (in my opinion, I prefer 0.25 here, but it should not be written as .25 as the decimal then is hard to spot). I always prefer tables or bullets above prose when a list of technical things w/numbers or w/attributes are being described, and I think that is the case here; however, I do think that this table could be a little more descriptive; I only wish I had more time but hopefully this helps...io_editor (talk) 23:49, 1 April 2008 (UTC)
 * Chiming in to agree with io io regarding the math and the use of a table. I'm thinking that the prose leading up to the table could be "de-condensed" a bit. Antelan talk  01:50, 2 April 2008 (UTC)
 * Progress! If pA is greater than pB, 1/(pB – pA) will be negative, so the absolute value of NNT is still greater than 1 but the sign will be negative rather than positive.  I prefer something between prose and the current table, namely blocks of "math" prose a la Diophantine equation.  The syntax is very similar to LaTeX, which I can do. --Una Smith (talk) 02:05, 2 April 2008 (UTC)
 * Yes, what you say technically is true, but it is generally meant in the context of drug v control (or placebo), and (usually, but not absolutely always!) it is known in advance that one should be greater than the other. As to your example, while I love the huge font, in my work I like ready-reckoner stuff like tables (plus my eye-sight tires) - maybe combine best of both worlds or ask Antelan...io_editor (talk) 02:36, 2 April 2008 (UTC)


 * Can we add a sentence that says if the treatment has the opposite effect (eg, people who take a drug to prevent heart attacks are unexpectedly more likely to have an MI than the untreated group), then you'll get a negative/nonsensical number (that is, a number smaller than zero)? I'm not sure that I can make what's clear in my head be sensible in words.  I strongly support including the equations.  (Please don't tell my math geeks.)  WhatamIdoing (talk) 06:13, 2 April 2008 (UTC)

If a treatment causes harm, then the NNT becomes an empty number (there is no "treating" being done). In fact, a negative NNT is the same as the number needed to harm (a parallel page on adverse effects, more properly named "number to treat to harm"). JFW | T@lk  11:37, 3 April 2008 (UTC)


 * Yes, but you're talking common sense, and I'm talking math. 1/(0.5-0.75) = –4, even if that doesn't mean anything in the real world.  Also, there's a divide by zero problem if there's no difference between the two groups.  I think this article should tell readers how to interpret these two cases.  WhatamIdoing (talk) 01:56, 4 April 2008 (UTC)
 * I agree. --Una Smith (talk) 02:01, 4 April 2008 (UTC)
 * Perhaps we should merge number needed to harm into this article, and mention that although the equations are identical, the label used depends upon the sign of the result. --Arcadian (talk) 00:00, 5 April 2008 (UTC)
 * I would say needless, as JFW was implying. In such circumstances (no "treating" being done, and possible harm) the tool is not usable - its an irrelevant formula, and is not an NNT of any kind.io_editor (talk) 18:27, 5 April 2008 (UTC)
 * I would merge, perhaps into Number needed; that would help to explain the bifurcation into harm and treat. --Una Smith (talk) 18:39, 5 April 2008 (UTC)
 * The bifurcation is only in the formula. In actual pratice there is no chain-of-logic that leads to a bifurcation. I dont mind if you merge them, but I think it will be a waste of your time better spent - and quite difficult too. Other pages need real work. See you.io_editor (talk) 19:49, 5 April 2008 (UTC)

External links removed
I removed all the ELs on this article, none of them were, particularly relevant. I pasted them below.


 * EBEM's Calculator for NNT
 * What is an NNT? (Hayward Medical Communications)
 * Number Needed to Treat (Centre for Evidence Based Medicine)
 * Online Calculator for NNT (GraphPad Software)

However, I do think these two are quite good. They should be worked into the article (inline references) instead of just dumped in the EL section. They should not stand on their own. Chaldor (talk) 00:39, 21 September 2008 (UTC)
 * Bandolier article on NNT
 * Number needed to treat (Slate)


 * I agree that some of these should be turned into proper refs. However, a link to a calculator is exactly the sort of thing that external links is intended for; it's the classic example of "a unique resource beyond what the article would contain if it became a featured article."  Consequently, I have restored those links.  (If someone wants to figure out which one is "better", then perhaps a single link would be sufficient.) WhatamIdoing (talk) 04:27, 21 September 2008 (UTC)


 * I figured out which one is better (they all were the same, so I chose randomly), and hence removed the remaining ones, as suggested. Psarka (talk) 22:49, 8 September 2018 (UTC)

Slate again
I'm of two minds about the inclusion of this link:


 * "Treat me? The crucial health stat you've never heard of", Darshak Sanghavi, Slate Magazine, Sept. 26, 2006

On the one hand, it's a better WP:RS than WP:EL. On the other hand, it "contain[s] information about the subject of the article from knowledgeable sources", and nobody's bothered to use it as a ref. Perhaps in the interest of providing some accessible sources for further information, it's inclusion wouldn't be such a bad thing -- at least until someone decides to expand this article. WhatamIdoing (talk) 20:24, 19 May 2009 (UTC)


 * This link is no longer included. Psarka (talk) 22:51, 8 September 2018 (UTC)

Hmm, kaboom
is a criticism of the NNT concept, and seems to indicate that ARR is a more useful statistical outcome. Why it got published in Br J Haem I do not know (possibly because haematology journals occasionally carry trials on antithrombotic and antiatherosclerotic treatments). I need to read this review and possibly include its findings in the article. JFW | T@lk  06:25, 11 June 2009 (UTC)


 * I will be interested in why they think that the ARR is more useful (I can't see the full study). I think of the NNT as being something that is a little easier for the public to grasp.  --stmrlbs | talk  06:58, 11 June 2009 (UTC)


 * That's pretty stupid Why would anyone...  Perhaps the authors can't do basic arithemetic in their heads?  Because that's the only possible reason for believing that "0.2" is materially different from "1 in 5", much less "better".  I'd have thought that professionals would be really embarrassed to admit that in public, but perhaps our pride in innumeracy has increased.
 * But I agree with their support for presenting baseline risk along with NNT/ARR, and for making the format of these two critical numbers match. I'd just present it in natural numbers instead of probabilities. WhatamIdoing (talk) 18:08, 15 June 2009 (UTC)


 * NNT = 1/ARR . If people don't like one, they can get the inverse pretty easily. At any rate, NNT is important for social justice concerns and for comparative outcomes research. Antelan  20:02, 15 June 2009 (UTC)


 * Not to mention that my patients actually understand me (no blank stare) when I use NNT to discuss benifit. Fuzbaby (talk) 04:05, 16 June 2009 (UTC)

Corrections/Explanation
Relative Risk is CER/EER Relative Risk Reduction is (CER-EER)/CER Absolute Risk Reduction is CER-EER Number Needed to Treat is 1/ARR

Or using a Punnett square, in which (a) has exposure & outcome, (b) has exposure but not outcome, (c) has outcome but not exposure, & (d) has neither outcome nor exposure: RR is (a/a+b)/(c/c+d) RRR is [(c/c+d)-(a/a+b)]/(c/c+d) ARR is (c/c+d)-(a/a+b)


 * It seems you´re incorrect or at least inconsistent: RR according to Punnett square is Experimental event rate to Control event rate, not hte other way around. T.pienn (talk) 13:47, 5 April 2014 (UTC)


 * Marking this as resolved. Psarka (talk) 22:54, 8 September 2018 (UTC)

Suggesting a total revamp of this article.
I was looking for online resources to help medical students study NNT and NNH for their board exams. I was hoping this page could be a useful educational resource.

NNT is not a very complicated concept, but this article makes it into one. It is not consistent with better-written Wikipedia articles on related topics(1). Useful components of this article are buried amidst distracting and irrelevant concepts(2). At least one example, should a reader attempt to replicate it themselves, appears erroneous or at least poorly explained(3). There are a few content points that I think are reasonable(4). I think it is unlikely that a reader would come away with an introductory working understanding of NNT after reading this article.

(1)Comparison to better-written articles: In general, the NNT article should probably be designed more similarly to it's better-written sibling article on "Number needed to harm." A reader should be able to flip back and forth between the two pages and correlate sections at a glance. This will make it easier to assimilate both topics and to highlight key differences between them.

(2)Useful components are buried amidst distracting and irrelevant concepts: The key definition of NNT (namely, 1/[(P(B)-P(A)] or 1/"absolute risk reduction") is buried in the middle of the "Derivation" section. This is, like, the punchline, folks.  It should be in large font on it's own line.  No-brainer.

Also: The third paragraph of the introduction describes the time-dependent nature of NNT. It uses a simple mathematical example. While it may be appropriate to mention the concept of time-dependence here, it doesn't make sense to get into math yet, when you haven't even defined NNT mathematically yet! By doing this, the article gets ahead of itself, and the reader is likely to trip.


 * "NNT values are time-specific. For example, if a study ran for 5 years and it was found that the NNT was 100 during this 5 year period, in one year the NNT would have to be multiplied by 5 to correctly assume the right NNT for only the one year period (in the example the one year NNT would be 500).[6]" - An underlying, dubious assumption here is that the successes and deaths are distributed evenly over the 5 years. This will be the case in some types of studies, but not in all. — Preceding unsigned comment added by 84.215.102.2 (talk) 14:49, 2 January 2014 (UTC)

Also: In the "Worked Example" section, "Number Needed To Treat" is buried on line 5 of 11 in the table. This table itself is peppered with concepts of questionable relevancy, variable abbreviations which are unnecessarily confusing, and it is visually crowded. Ok, that's being too nice. It's a nightmare. This is a huge failure of style.

(3)An example appears erroneous: (in the "Example: statins" section) "Taking atorvastatin for 3.3 years, therefore, would lead to an ARR of only 1.02% (2.67% minus 1.65%). The number needed to treat to prevent one cardiovascular event would then be 99.7 for 3.3 years" Ok, lets follow the math on this one. 1 / (0.0267 - 0.0165) = 1 / 0.0102 = 98.03921... This does not equal 99.7. In fact it is completely unclear where 99.7 came from, although it is cited to references [10] and [11]. Checking these references I could not find this number in a proper context. Never mind the fact that BusinessWeek has no business here, if this is, in fact, intended to be a paragraph on a didactic example. (If you want this to merely be a "NNT-example-in-society" example, BusinessWeek might be useful as an example of how a non-technical publication can over-simplify a nuanced controversy. And why on earth BusinessWeek?  Just because they wrote a simplistic article on NNT doesn't mean it's an appropriate resource.  But I'm getting sidetracked.)

Maybe I'm missing something critical in point in the math on #3 here. But regardless of whether it is technically correct or not, a reasonable reader, following the concepts of this article, would be inevitably lead to this inconsistency. And sadly, this is the most clear example of NNT in the whole article.

Furthermore: the use of statins alone as the "real world example" is dubious because there is some mild controversy in the medical community (despite the fact that everybody prescribes them)-- the controversy is a little too technical and esoteric for the average reader to appreciate or care about. Better, simpler examples exist, and the topics of both medical prevention and medical treatment should be represented. If someone out there really loves the statin controversy and wants to keep this in, that is fine with me, but lets not "wag the dog" here. The statin concept should come after a simpler example of an acute treatment (with an NNT in the 2-4 range) and another example of a prophylactic measure with a higher NNT.

(4) reasonable content: The major content topics are appropriate and I think they'd be useful to consider in a complete re-write.

Conclusion: This article suffers greatly from poor style, irrelevant distractors, absense of appropriate content, and possibly a gross mathematical error. Unless I hear anyone chime in, within in a reasonable amount of time, I'm going to re-write the whole blasted thing. [MSS 3/3/2012]


 * I'm not an expert on the subject, but I am not surprised you found that it could benefit from a re-write. Let me know if you have any questions or run into any issues while you contribute to the article. Biosthmors (talk) 16:54, 5 March 2012 (UTC)


 * (1) NNT is currently in much better shape than NNH. (2) Formula is now in the definition, time based stuff is gone, and table has been improved. (3) Math error was fixed. BusinessWeek reference is indeed weird, but there seem to have been a fight over it already, so let's keep it. (4) whole article seems to be reasonable now. Psarka (talk) 23:01, 8 September 2018 (UTC)

positive as well as negative events
It is interesting to note that while your article adopts the usual idea that the event is the undesirable aspect for each group, some sites, such as the Bandolier one, uses the desirable outcome as the event and subsequently changes the equations - might be worthwhile to point out.

Also some sites define ARD as the (absolute =modulus) and RD as the value that can take a negative value. This can be useful in explaining simply that a negative NNT is in effect a NNTH, but obviously only if you use the ARD true and not the absolute value. — Preceding unsigned comment added by 80.229.171.143 (talk) 11:42, 18 February 2013 (UTC)

A minus sign is not a hyphen
I found this twice in this article:
 * -10

It appeared to mean minus 10. I changed it to this:
 * −10

That is a proper minus sign. If used to indicate one number subtracted from another it should be formatted like this:
 * 20 − 10

with a blank space to its left and one to its right. 2601:2:4D00:27B:5582:2521:6AB:4186 (talk) 16:11, 8 October 2014 (UTC)


 * Thanks! Psarka (talk) 23:03, 8 September 2018 (UTC)

Asprin example
How about another example with aspirin. The New York Times explains it in easy to understand terms. The Wikipedia article is written by statisticians for other statisticians. --Richard Arthur Norton (1958- ) (talk) 18:03, 6 February 2015 (UTC) http://www.nytimes.com/2015/02/03/upshot/how-to-measure-a-medical-treatments-potential-for-harm.html?


 * I think one example is enough. Psarka (talk) 23:04, 8 September 2018 (UTC)

Time as a factor
How is time-to-cure or time-to-heal taken into account? Suppose you have a condition that without treatment lasts from ten to twenty days, uniformly distributed, but the treatment shortens this period by five days for half of the patients and shortens it by a factor of two for the other half. What would be the NNT in that case? Vaughan Pratt (talk) 01:13, 19 February 2018 (UTC)

Caption wrong?
Right now, the caption for the first image is "Group exposed to a treatment (left) has reduced risk of an adverse outcome (grey) compared to the unexposed group (right). 4 individuals need to be treated to prevent 1 adverse outcome (NNT = 4)." Is that correct? From my understand, the adverse outcome would be colored in red as there are more "greys" in the (effective) treatment group. Or am I missing something? 2A02:908:D78:D1A0:3058:DE3D:230B:77EF (talk) 18:15, 23 February 2023 (UTC)