1 - The level of water usage of 250 houses was rated in a survey as low, medium or high and the size of the houses as small, standard or large. The variables, level of water usage and size of house, as recorded in this survey, are a. both numerical variables. b. both categorical variables. c. neither numerical nor categorical variables. d. numerical and categorical variables respectively. 3- For a very rare disease, odds ratio is equal to: a. Likelihood ratio b. Positive Predictive value c. Negative Predictive value d. Relative risk 4- The sensitivity of a clinical test: a. Refers to the ability of a test to identify patients without the disease. b. Depends on the prevalence of the disease in the population. c. Should be as high as possible when screening for a serious, preventable or treatable condition. d. Defines how likely it is that a patient who tests positive has the condition 5- The interpretation of Odds ratio > 1 is a. Decreased frequency of exposure among cases b. No change in frequency of exposure among cases c. Increased frequency of exposure among cases d. None of the above