A Researcher Would Like to Determine If Relaxation Training Will

A researcher would like to determine if relaxation training will affect the number of headaches for chronic headache sufferers.For a week prior to training,each participant records the number of headaches suffered.Participants then receive relaxation training and for the week following training the number of headaches is again measured.The data are as follows: $$\begin{array} { l l } \text { Before } & \text { After } \\6 & 4 \\5 & 1 \\3 & 3 \\3 & 1 \\6 & 2 \\2 & 1 \\4 & 3 \\4 & 2 \\\hline\end{array}$$
a. Compute the mean and variance for the sample of difference scores.
b. Do the results indicate a significant difference? Use a two-tailed test with α = .05.
c. Compute Cohen's d to measure the size of the effect.