Hypothesis testing using paired-samples t-test

4. A sample of 5 rats are given a drug that has been designed to improve memory. The rats are tested in a water maze task prior to receiving the drug and then after. Their latency to solve the task (in seconds) is the dependent variable, with a faster (smaller) time inferring better memory. Conduct a paired-samples t-test and compare it to the critical t-value to determine if the difference is significant. Assume a two-tailed hypothesis with = .05. Based on these results what can we infer about the effect that the drug had on the rats' memory? (3 marks)

Pre-drug Post-drug

Rat 1 18 22

Rat 2 24 24

Rat 3 20 30

Rat 4 16 20

Rat 5 26 33

Calculate the effect size (i.e., Cohen's d) and indicate the relative size of the effect. (1 mark)