a. What are the research reliability and validity? What is internal validity and construct validity? What are the difference between reliability and validity?

b. Please describe research hypothesis and statistical hypothesis. What are the difference between these two kinds of hypotheses?

c. What are three level of research? Exploratory research, descriptive research and explanatory research? What are the difference between them?

d. What are case-control design, nested case-control design, and cohort design? What are the difference between case-control design and population-based case-control / nested case-control design, and cohort design?

e. Please define the relative risk (RR) and odds ratio (OR). What is the difference between relative risk and odds ratio?

f. Please describe the number needed to treat (NNT) and number needed to harm (NNH). What is the difference between NNT and NNH?