In an Experiment Aimed at Evaluating the Effect of a Memory-Enhancing

Multiple Choice

In an experiment aimed at evaluating the effect of a memory-enhancing drug on the recall of a previously learned response. Either the drug or a placebo was administered to different groups of rats before the memory test. There were three trials of the memory test, and the dependent variable was the time it took the animal to make the correct response.
We want to compute an effect size estimate for the difference between drug and placebo treatments. We will take as our dependent variable for this computation each animal's mean response time over the three trials. What would be the best estimate of effect size?

A) The difference between the means of the two groups.
B) The difference between the group means divided by the square root of the pooled variance estimate.
C) The difference between the means divided by the standard deviation of the control group.
D) None of the above would be of any value.