Talk:Factorial experiment

Untitled
I don't think the example given here is actually an experiment. It's a retrospective study. Michael Hardy 22:05, 1 May 2005 (UTC)


 * Well, given that I failed Stats II in college, I'm no expert at this. :) This article was merely the result of some Googling; feel free to rewrite it as you deem necessary.  --Fbriere 22:22, 1 May 2005 (UTC)


 * "given that I failed Stats II in college" -- shouldn't that be in a banner at the top?--John Bessa (talk) 18:06, 20 May 2011 (UTC)

Thanks for an interesting article! — Charles Edwin Shipp (talk) 23:39, 4 July 2013 (UTC)

Does this topic have any relationship to factorials in mathematics, or is the name referring purely to the fact that there are multiple variables ("factors") being considered? If the latter, I think a "not to be confused with" hat-note might be good. Cesiumfrog (talk) 00:22, 11 August 2014 (UTC)


 * I've added an "About" note at the top of the article with a link to the article about factorial numbers. Johsebb (talk) 20:24, 17 February 2023 (UTC)

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Main effects and interactions; Components of interaction
On December 6, 2022, I added the section “Main effects and interactions,” and have modified it slightly since then. I am now doing three things:
 * Rewriting it to make it more accessible and to integrate it better with the pre-existing article.
 * Adding a set of references and changing all citations to the short form using harvtxt.
 * Adding a new section, “Components of interaction.”

Both sections contain links to places in other Wikipedia articles. What I have been unable to do is to arrange it so that hovering the cursor over those links shows the actual target location of the link, and not the beginning of the target article. I would be very pleased if someone took on that job. Johsebb (talk) 20:32, 21 March 2023 (UTC)


 * I am removing this section, as well as the new section "Components of interaction." They are not written in encyclopedia style (but rather in textbook style).  "Components of interaction" does not belong in this article, and will hopefully go in a future article on "Confounding with blocks."
 * I have rewritten the section on Main effects and interactions (now called "Contrasts, main effects and interactions"), and placed it after "Notation" rather than after "Implementation". I have endeavored to stick to encyclopedia style.
 * I have added one reference, as well as a section of "Explanatory notes".
 * After I publish these changes, I will replace the Notation section, which is inadequate. Johsebb (talk) 03:21, 25 February 2024 (UTC)

Error in use of harvtxt (loc parameter)
In the final paragraph of the Components of interaction section, I initially had this citation: This created an error message due to multiple targets (of the loc parameter, I assume). I tried changing the semicolon to a comma or to the word "and", but the error has persisted. I heartily invite someone smart to fix this.

In this citation I am referring simultaneously to two sections of this reference, and I'm using their titles (rather than section numbers) to make this citation independent of the particular edition of this text. I don't think this should matter. Johsebb (talk) 21:10, 21 March 2023 (UTC)

Analysis issues
The analysis example given (a $$2^4$$ design with one observation per cell) has several problems:
 * The block quote allegedly from Montgomery is not in the 8th edition. Perhaps it's from another edition.


 * After the initial analysis, the design is projected on three factors (A, C, D) and re-analyzed, but projection is not mentioned or explained, the table labeled ANOVA is not an ANOVA table, and the analysis is different from Montgomery's (compare his Table 6.13). This needs some significant rewriting.

The analysis section points to Yates analysis as the "main article", but Yates analysis is an algorithm for computing quantities used in analysis. This link should be at the end as "see also". Johsebb (talk) 16:15, 19 April 2023 (UTC)

"When the factors are continuous, two-level factorial designs assume that the effects are linear. If a quadratic effect is expected for a factor, a more complicated experiment should be used, such as a central composite design." Missing is any suggestion of using factors with 3 or more levels. — Preceding unsigned comment added by Johsebb (talk • contribs) 16:09, 20 April 2023 (UTC)

Two-level and multi-level designs
The original article concentrated almost exclusively on two-level designs. I inserted material on multi-level designs to correct this. It would be useful to have an ANOVA example for, say, a 2x3x3 experiment.

The claim that in " the vast majority of factorial experiments, each factor has only two levels" is unsupported. It may be that two-level designs are the most popular. Johsebb (talk) 16:18, 19 April 2023 (UTC)

Notation section revised
The original Notation section was inadequate, dealing only with two-level designs and in a very incomplete manner. I had added a paragraph to it to explain notation in general designs, but this was written in math text style and was thus very inappropriate. The new section is written (I believe) in encyclopedia style. It is written to support the rest of the article, especially the section on "Contrasts, main effects and interactions." Johsebb (talk) 03:33, 25 February 2024 (UTC)

Box/Hunter/Hunter citations
I have retained both editions of this text in citations. The footnote near the end of refers to a quotation from the original (1978) edition that did not find its way into the second edition. Johsebb (talk) 18:36, 6 March 2024 (UTC)