11q: prevalence of a disease :
a. is the best measure of the disease frequency in etiological studies
b. can only be determined by a cohort study
c. is the number of new cases in a defined population
d. describes the balance between incidence,mortality and recovery
12q: in a controlled trial to compare two treatments , the main purpose of randomization is to ensure that :
a. the two groups will be similar in prognostic factors
b. the clinician does not know which treatment the subjects will receive
c. the sample may be referred to a known population
d. the clinician can predict in advance which treatment the subjects will receive
13q: a randomized trial comparing the efficacy of two drugs showed a difference between the two with a p value of less than 0.005. in reality however the two drugs do not differ . this is therefore an example of ?
a. type 1 error ( alpha error )
b. type 2 error ( beta error )
c. 1- alpha
d. 1- beta
14q: the number of patients required in a clinical trial to treat a specific disease increases as :
a. the incidence of the disease decreases
b. the significance level increases
c. the size of the expected treatment effect increased
d. the drop out rate increases
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