Use the tool to evaluate the null hypothesis; using t-tables without exact degrees of freedom may not lead to an answer with enough precision. (Note: You can place the purple line on your t statistic to tell whether it lies within or outside the critical region. It's possible that this line may not rest exactly on the t statistic, but you will be able to tell whether it lies within or outside the critical region.) The t statistic in the critical region for a two-tailed hypothesis test. Therefore, the null hypothesis is . The graduate student conclude that viewing nature scenery affects working memory. The graduate student repeats his study with another random sample of the same size. This time, instead of the treatment being walking in a nature setting, the treatment is walking on a treadmill. Suppose the results are very similar. After walking on a treadmill, the mean score was still 0.9 lower, but this time the standard deviation of the difference was 1.4 (vs. the original standard deviation of 1.8). This means has the more consistent treatment effect