When deciding on the form of the alternative hypothesis, H1, remember that a positive difference score (D = X1 €“ X2) reflects a decline in cigarette consumption.)
(a) Using t, test the null hypothesis at the .05 level of significance.
(b) Specify the p - value for this test result.
(c) If appropriate (because the null hypothesis was rejected), construct a 95 percent confidence interval for the true population mean for all difference scores, and use Cohen€™s d to obtain a standardized estimate of the effect size. Interpret these results.
(d) What might be done to improve the design of this experiment?