[R] Means do not tally
Ruijie
breakaway8 at gmail.com
Mon May 24 18:54:10 CEST 2010
Thanks for your help jim. I have attached the raw data to see if anyone else
can replicate my problem.
Regards,
Ruijie (RJ)
--------
He who has a why can endure any how.
~ Friedrich Nietzsche
On 25 May 2010 00:17, jim holtman <jholtman at 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 <breakaway8 at 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 <jholtman at 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 <breakaway8 at 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 at 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?
>
More information about the R-help
mailing list