Answers to Practice Questions for Final:

(annotated with side comments in places)

Part V:

Part V: INTERPRETING SPSS OUTPUT

Under group statistics, you should definitely note the "n"s for the two groups (a small n study, so limited power) and look at the means (FTF higher) so you'll know what direction the difference is in if the test is significant. Comparing the Std. Dev. will give you a sense of whether variances are reasonably equal, but the next bit of data gives you a more precise decision about whether or not equality of variances can be assumed. Circle the significance level. NOT significant at .05 level, which is GOOD news -- in this case you are hoping that the null hypotheses of "equal variances" is NOT rejected. Note in margin something like "NS -- passed test" or "Good--equal variances test okay"

Now you know which set of results to look at for the actual t-test (by default, SPSS always runs it both ways, for equal variances assumed or not). Mark which row we should look at. Circle the t, df, and significance, checking to see if the test came out significant, and if so, at what level. In this case, I'd write "NS" next to the significance level. If the test WAS significant, I would put a star next to it or write "p < .05 ... or .01 or .001 or however it turned out [there's not a "fixed" way to annotate -- what's important is that you draw attention to the key information here]

Sample Paragraph I would write to the non-SPSS savvy but statistically literate reader:

The output shows that there was no significant difference between the two groups, using a t-test for independent samples, t ₍₂₈₎ = .227, NS. [taking info from output and turning into standard notation] The FTF groups did have higher performance scores overall than CMC groups (mean of 63.6 versus 57.7) but this difference was not significant. This was a small N study, however, (14 FTF groups, 16 CMC groups) so the power is low. Thus there may well be a difference, but our power is too low to confirm it at the 95% confidence level.

[Your paragraph might be worded very differently: the important thing here is that it should convey all the key information about the results of the test]