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 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 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 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 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?
>>
>
>
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