Week_7_prep_for_t_test_rev_3_8_08

Week_7_prep_for_t_test_rev_3_8_08 - SAN JOS STATE...

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SAN JOSÉ STATE UNIVERSITY College of Social Work S. W. 242 Spring 2008 Edward Cohen Prep for t -test Example of Independent Sample t -test with randomly assigned groups Consider the following data. “Treatment” is a variable indicating assignment to experimental treatment (coded “1”) or treatment-as-usual (coded “2”). “Pre-test anxiety score” and “Post-test anxiety score” are from a ratio-level anxiety scale, where lower scores indicate lower anxiety. We are interested in the change in anxiety as a result of treatment, from pre- to post-. We will be comparing both groups on a “Change score” that we will compute with SPSS. (Note: even though this example uses repeated measurements, we will be using the Independent Sample t -test. We could also use a Dependent sample t- test, running it twice— once for each treatment group , to compare the pre- post-test score for each treatment group. Why would it be better to compute the change score and then use the Independent groups t -test on that variable? Treatment Pre-test anxiety score Post-test anxiety score Change score (to be computed) 1.0 10.0 8.78 1.0 11.85 9.0 1.0 8.0 10.88 1.0 7.5 5.5 1.0 11.99 7.7 1.0 12.34 12.05 1.0 10.8 9.0 1.0 9.8 7.78 1.0 5.46 5.58 1.0 12.80 8.5 1.0 13.9 8.0 1.0 7.79 7.6 1.0 8.03 7.79 1.0 12.85 10.89 1.0 13.88 12.07 2.0 10.0 10.89 2.0 11.85 10.08 2.0 8.0 9.9 2.0 7.5 7.77 2.0 11.99 10.78 2.0 12.34 12.0 2.0 10.8 11.88 2.0 9.8 9.78 2.0 5.46 6.0 2.0 12.80 12.05 2.0 13.9 13.93 2.0 7.79 7.5 2.0 8.03 8.4
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2.0 12.85 12.0 2.0 13.88 12.5 Once the data for the three variables are entered into SPSS, let’s compute the Change Score: In SPSS Data View, go to
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This note was uploaded on 09/08/2010 for the course SCWK 242 at San Jose State.

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Week_7_prep_for_t_test_rev_3_8_08 - SAN JOS STATE...

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