data analysis bug

["Andreas J. Guelzow" <aguelzow math concordia ab ca>]

I guess I should really file an official bug report but here is the 
short form:

The pooled variance calculated for the "T-test: Two Sample Assuming 
Equal Variances" is not always correct:

sample 1: 1,2,3
sample 2: 1, 2.2, 3.4

individual variances are 1 and 1.44. The pooled variance is a weighted 
average of those two, ie. must be lying between 1 and 1.44 (in fact it 
is 1.22), but gnumeric calculates 0.988

This will normally also affect the t statistic etc. I didn't check 
whether they were incorrect but since they should use the pooled 
variance....

This is today's CVS version of gnumeric. (But I observed the same 
problem in an earlier version while using gnumeric in an introductory  
statistics class this May.)

Andreas



--
Prof. Dr. Andreas J. Guelzow                    
Assoc. Prof of Mathematics
Concordia University College of Alberta
http://www.math.concordia.ab.ca/aguelzow