Wikipedia:Reference desk/Archives/Mathematics/2011 May 14

= May 14 =

Statistics text
Hello. I'm looking for a good, rigourous, calculus-based introductory statistics text. It should start from the very basics (i.e., assuming you don't even know what a mean is [though I do], not basic as in starting from field theory because that is too basic :), kind of an equivalent to Spivak's calculus text. Does anyone have any recommendations? Thanks. 72.128.95.0 (talk) 15:37, 14 May 2011 (UTC)
 * I don't really know a lot of statistics textbooks, but you can try All of statistics. It starts at the beginning, but it's very condensed, it tries to cover a lot of technical ground without too much discussion. -- Meni Rosenfeld (talk) 08:28, 15 May 2011 (UTC)

De Groot. (Not "equivalent to Spivak's Calculus", but addressed to somewhat mathematically inclined readers.) Michael Hardy (talk) 22:02, 16 May 2011 (UTC)

Simple formula tom figure out kilobytes per second to number of hours?
Can anyone give me a simple formula to figure out how long it will take to download a file given a constant number of kilobytes per second and knowing the total size of the file in gigabytes? It would be easier for me to see the calculation I think with a real example so say I am downloading at a constant rate of 92 kilobytes per second and the file I am downloading is 13.4 gigabytes. I know I have to do something like multiplying the number of kbs by 60 to get to minutes and then 60 to get to hours and then dividing somehow into the number of gbs expressed in kbs but I get lost in the details. Thanks.--108.54.17.250 (talk) 15:12, 14 May 2011 (UTC)


 * You divide the file size by the download rate to get the number of seconds. Divide by 60 to get minutes, and by 60 again to get hours. In your example, you have 13.4 gigabytes = 13400000 kilobytes divided by 92 kilobytes/second to get 145652 seconds. Divide by 60 seconds/minute to get 2427 minutes. Divide by 60 minutes per hour for 40 hours. Detailed numbers are slightly different if you use base-2 gigabytes, instead of base 10, and if you don't just drop fractions. --Stephan Schulz (talk) 16:30, 14 May 2011 (UTC)
 * Great. Thank you. So its convert file size in gb → kb/kbs/60/60.--108.54.17.250 (talk) 16:42, 14 May 2011 (UTC)


 * To put it as simply as possible, divide the file size (in gigabytes) by the download rate (in kilobytes per second), and then multiply the result by 278 -- this will give you the time in hours. (Reason: 1 GB/hr = 278 kB/sec)Looie496 (talk) 17:00, 14 May 2011 (UTC)


 * Be careful mind, some transfer rates are given in kilobits per second (kbit/s, kb/s, or kbps) and there are 8 kilobits to the kilobyte. Grandiose (me, talk, contribs) 17:04, 14 May 2011 (UTC)


 * To further complicate things, often people write "gigabyte" when they really mean gibibyte. Also (though this may be irrelevant for the OP), sometimes the electrical bitrate is specified, and with 8b/10b encoding one data byte is 10 electrical bits. -- Meni Rosenfeld (talk) 08:21, 15 May 2011 (UTC)


 * Note that if you actually attempt to download 13.4 GB, your ISP is likely to stop you or slow the transfer rate down to a crawl. And, even if they don't, the download is likely to be interrupted anyway, so you need a way to restart an interrupted download. StuRat (talk) 04:17, 16 May 2011 (UTC)

Google:. Sławomir Biały (talk) 12:09, 16 May 2011 (UTC)