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

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