Thanks for your help jim. I have attached the raw data to see if anyone else can replicate my problem.
Correction: i realise my attachment was too large, I have uploaded it to another site. The link is: http://dl.dropbox.com/u/1443460/List%20-%20Raw%20Data.csv Regards, Ruijie (RJ) -------- He who has a why can endure any how. ~ Friedrich Nietzsche > > > On 25 May 2010 00:17, jim holtman <jholt...@gmail.com> wrote: > >> Are you sure that you have the same number of data points in each of >> the summary cells that you show in your csv file that was sent? You >> need to provide a reproducible example of all the data so we can see >> what you did. The best information I can provide at this point is >> that you have a "bug" in your calculations. >> >> On Mon, May 24, 2010 at 11:10 AM, Ruijie <breakaw...@gmail.com> wrote: >> > Noted. >> > >> > I have attached a list of some data in csv format. >> > >> > The first column is the SubID and the rest of the column are the mean of >> > each condition for the particular subject. >> > >> > Average 1 is the average computed from each column in the list. >> > Average 2 is computed from the raw data of all the data points of a >> > condition. >> > >> > The difference is typically at the 3rd decimal place. If anyone needs >> the >> > raw data, I could supply it after some clean up. >> > >> > I suspected round of errors but in all procedures in R, I retained 14 >> > significant figures. How would the round off error affect the 3rd >> decimal >> > place? >> > >> > Any ideas anyone? >> > >> > Regards, >> > Ruijie (RJ) >> > >> > -------- >> > He who has a why can endure any how. >> > >> > ~ Friedrich Nietzsche >> > >> > >> > On 24 May 2010 22:47, jim holtman <jholt...@gmail.com> wrote: >> >> >> >> It is hard to tell what you are doing without data and the results you >> >> have gotten so far: >> >> >> >> PLEASE do read the posting guide >> >> http://www.R-project.org/posting-guide.html >> >> and provide commented, minimal, self-contained, reproducible code. >> >> >> >> >> >> On Mon, May 24, 2010 at 10:35 AM, Ruijie <breakaw...@gmail.com> wrote: >> >> > Hi all, >> >> > >> >> > here is my situation >> >> > >> >> > In my experiment, I expose 10 subjects to 24 different conditions of >> >> > stimuli. Each condition is exposed to the same subject 3x. >> >> > This would make each subject have 24x3=72 data points. All the >> subjects >> >> > combined would have 72x10=720 data points with each condition having >> 30 >> >> > datapoints. >> >> > >> >> > To find the grand average of each condition, I find the average of >> all >> >> > the >> >> > datapoints for a given condition. >> >> > >> >> > To find the SD for each condition, if I use the raw dataset (720 >> >> > datapoints) >> >> > it would not reflect the SD across subjects. Therefore, I compute the >> >> > average for each condition per subject .i.e. For subject 1, I would >> find >> >> > the >> >> > average of condition 1 (average across 3 trials). and so on. >> >> > With the average of each condition per subject, I then compute the >> SD. >> >> > >> >> > Since I computed the average of each condition per subject, >> >> > theoretically, >> >> > if i average the average of each condition per subject across all >> >> > subjects, >> >> > the result would be the same as the grand average. >> >> > >> >> > However, this is not the case when I use R or Excel. regardless of >> >> > functions >> >> > used. Anyone have any thoughts? >> >> > >> >> > Regards, >> >> > Ruijie (RJ) >> >> > >> >> > -------- >> >> > He who has a why can endure any how. >> >> > >> >> > ~ Friedrich Nietzsche >> >> > >> >> > [[alternative HTML version deleted]] >> >> > >> >> > ______________________________________________ >> >> > R-help@r-project.org mailing list >> >> > https://stat.ethz.ch/mailman/listinfo/r-help >> >> > PLEASE do read the posting guide >> >> > http://www.R-project.org/posting-guide.html >> >> > and provide commented, minimal, self-contained, reproducible code. >> >> > >> >> >> >> >> >> >> >> -- >> >> Jim Holtman >> >> Cincinnati, OH >> >> +1 513 646 9390 >> >> >> >> What is the problem that you are trying to solve? >> > >> > >> >> >> >> -- >> Jim Holtman >> Cincinnati, OH >> +1 513 646 9390 >> >> What is the problem that you are trying to solve? >> > > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
