1) Advantages of random sampling for studying the general human population include:

2) In a case-control study to investigate oral contraception and breast cancer:

3) In a case-control study, patients with lung cancer had a highly significantly lower cholesterol level than did controls. This provides strong evidence that:

4) The paired t test is:

5) For a t test for two independent samples to be valid:

6) A simple linear regression equation:

7) The product-moment correlation coefficient between two variables, r:

8) The standard chi-squared test for a 2x2 contingency table is not valid unless:

9) To analyse the relationship between blood pressure and height in a sample of students, we could use:

10) In a case-control study, 101 stroke patients were compared with 137 healthy controls. Among the results were: Cigarette smoking by stroke patients and healthy controls - Ever smoked? Cases: 71 yes, 30 never, 101 total; Controls: 36 yes, 101 never, 137 total; Chi-squared = 45.5, 1 degree of freedom, P less than 0.0001, Odds ratio = 6.6 (95% confidence interval = 3.8 to 11.8)