4. Investigations in which the student units are stimulated in some way and the researcher observes a response is called ( 1 mark) a) Observational studies b) Prospective studies c) Sample studies d) Experimental studies e) Retrospective studies

5. Investigators who us nonrandomized controls in clinical trials often argue that their controls are satisfactory because the distribution of prognostic factors in the control and experimental groups is similar before therapy. It is better to randomize because (1 mark) a) A placebo effect s easier to detect in randomized trials b) Randomization tends to magnify the differences between placebo and treatment groups c) Many important prognostic factors that were not considered may lead to bias d) It is easier to maintain blinding in randomized trails e) Compliance is better in randomized trials

7. A combination drug has two components. A. the antihistamine and B the decongestant. A clinical trial is designed in two parts: part 1 to randomly assign patients to either a placebo control or drug A, and part II to randomly assign a second group of patients to a placebo control or drug B. A more efficient plan is to use a design with a (1 mark) a) 2 stage cluster sampling b) Systematic random sample c) Good compliance history d) Random allocation of adverse drug experiences e) Factorial arrangement of treatment