st: how to check the reliability and validity of the data

["George Huang" <cj0623@thu.edu.tw>]

Dear all:

I have a database with 72,878 observations which can be grouped into 2,800 
average time of different activities. Therefore, there are 2,800 means and 
2,800 S.D. for the activity time. How can I know the reliability and 
validity of each activity time? Should I use nonparametric statistics or 
chisquare test?

Thanks a lot for your help!

George Huang 
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