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I'm after a little advice; I have data collected during experimentation that was designed to determine the improvement of two groups of subjects between a pre and a post-test. The results are as follows:

Pre & Post test numbers represent the number of errors made

Group 1:

Code (Text):

Pre|Post|Improvement

0 0 0

1 0 1

5 4 1

12 0 12

2 0 2

7 6 1

0 0 0

13 0 13

Group 2:

I'm applying the t-test to determine if there is a statistical difference between the means(of the improvement columns).Code (Text):

Pre|Post|Improvement

0 1 -1

2 0 2

1 0 1

0 0 0

0 11 -11

5 23 -18

My question is really simple(hopefully)... in group 2, should I be recording improvement as a negative number? or simply zero?

Using zero will not give me a significant statistical difference between the means of group 1 and group 2... using the negative numbers does.

Also, if I'm keeping the negative improvement numbers, is it okay to represent improvement as a negative percentage?

I've not done much with statistics, so would appreciate your input.

Thanks,

Craig.

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# Pre-Post Test Improvement

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