SUGGESTED ANSWER TO QUESTION 2B-2

This is not good evidence because the effects of two extraneous variables were not being controlled: placebo effects and experimenter bias. In order to control for the effects of these extraneous variables, the study needs to include a placebo-control group--a group that is treated identically to the experimental (treatment group) except that a placebo is given rather than the anxiolytic medication. The experiment also needs to be performed in a double-blind manner. If, after doing this, a larger average decrease in anxiety is observed in the experimental group compared to the control group, then the researchers can conclude that the medication is effective for reducing levels of anxiety.