[R] summing values according to a factor

Salvatore Enrico Indiogine hindiogine at gmail.com
Mon May 7 05:59:41 CEST 2007


I have exam scores of students in several sections.  The data looks like:

StuNum Section Q1  T1
111           502     45   123
112           502     23    123
113           503     58    123
114           504      63   123
115           504      83   123

where Q1 is the score for question 1 and T1 is  the maximum possible
score for question 1

I need to check whether the section has an effect on the scores.  I
thought about using chisq.test and calculate the sums of scores per

I think that I have to use apply() but I am lost here.

Thanks in advance,

Enrico Indiogine

Mathematics Education
Texas A&M University
hindiogine a gmail.com

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