The group of 23 bully-victims scored an average of 40.1 with a sample standard deviation of 10 on the depression scale. The group of 28 bystanders scored an average of 46.8 with a sample standard deviation of 11 on the same scale. You do not have any presupposed assumptions about whether bully-victims or bystanders will be more depressed, so you formulate the null and alternative hypotheses as:

Null Hypothesis = Depression levels among two groups equal, Alternate Hypothesis = Depression levels among two groups unequal.

Step-by-step explanation:

Null Hypothesis is the neutral hypothesis, of no difference.

Null Hypothesis in this case is, mean depression level among victims = mean depression level among bystanders.

Alternate Hypothesis in this case is, mean depression level among victims ≠ mean depression level among bystanders.