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I really suck at this so hope you could help me

ve a group of people attending a training course, in order to measure whether the training course is effective in improving attendees' knowledge. We did the following:

attendees will complete a pre-test (TRUE or FALSE only) before the training
attendees attending the training
attendees will complete a post-test (TRUE or FALSE only) after training

Both pre and post tests are having exactly the same questions, However the test is NOT tagged with barcode so i have NO way to know if a certain pre and post questionnaire belong to the same individual

Each paper has been scored out of 20 ,, and the scores i have entered in SPSS for every student for both the pre and post questionnaire

So for this can i just use the paired t test and will the interpretation still be valid or is there an alternative i can use to find the significance of the intervention and whether it was effective or not? or should i do the t-test to the sum of the scores for pre and post?

Thanks alot

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  • $\begingroup$ You can't use the paired t-test in this case, standard t-test will have to be it. $\endgroup$
    – Affine
    Commented Mar 26, 2014 at 18:18
  • $\begingroup$ Also, since presumably the goal is to measure if there is an impact of training on test scores - having the post-test have the same questions as the pre-test will cloud the interpretation (is it really the training that improved scores or familiarity with the test?) $\endgroup$
    – Affine
    Commented Mar 26, 2014 at 18:19
  • $\begingroup$ Thanks ,, but how can the familiarity with the test affect the scores ? because the only way someone can get a better score is if they have improved their knowledge via the intervention which was done or through luck by chosing randomly a different answer - so that way i can know if my intervention was generally effective or not $\endgroup$
    – Ahmad
    Commented Mar 26, 2014 at 18:25
  • $\begingroup$ Familiarity with the test format can help. For example, there's a well-known "bump" in SAT scores when students re-take the exam, even if they haven't studied. The actual questions are different, but students now know a bit more about the structure of the test. $\endgroup$
    – Matt Krause
    Commented Mar 26, 2014 at 18:28

1 Answer 1

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How would you go about pairing them? A paired t-test asks whether the mean difference between paired observations is different from zero. For example, you might weigh people, put them on a diet, and then weigh them again some time later. An unpaired t-test would ask whether the average weight of the "before" group differs from the average weight of the "after" group. A paired t-test, however, compares each person's weight loss/gain.

It doesn't sound like you have any sensible way of pairing your questionnaires, so you cannot use a paired t-test. This isn't necessarily the end of the world--you can use an unpaired t-test instead: this would tell you whether there was a significant different in the two total scores.

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