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View Full Version : Experimental group and .. which control group?


michael1234
02-26-2010, 10:58 AM
Hello.
I have data from pre and post tests of 10 classes of 20 students per class.
However, one class of 20 students participated in a semester-long experiment which other 9 groups did not. So my question is:
Do I compare the experimental group with each of the other 9 groups one by one OR compare the experimental group to all students (where sample sizes (Ne=20 and Nc=180) will obviously be hugely different)?

Any other related advice about what to look for will be greatly appreciated.

Thank you in advance.
Michael

omega
03-02-2010, 02:07 AM
Students in the same class are correlated. I would compare by classes.