17. A nurse intends to establish risk factors for a rare disease, the best design to use is"- a. Cohort b. Case-control c. Cross sectional d. Case series 18. The most basic epidemiological study design is:- a. Ecological study design b. Case report study design c. Case series study design d. Cross sectional study design 19. The major determinants of demography are:- a. Size, structure and distribution of populations b. Migration, mortality and morbidity c. Migration, mortality and fertility d. Crude birth rate, crude death rate and life expectancy 20. Rates computed by eliminating the effect of differences such as age distributions in the populations being studied are referred to as: a. Crude rates b. Age specific rates c. Adjusted rates d. Proportionate rates 21. The main difference between interval and ratio measurement scales is that an interval scale: - a. Is used for discrete data b. Has no meaningfu I point zero c. Is used for nominal data d. Has unknown distance between values 22. The following is correct about the mode: a. There can only be one mode in an array of data b. It should not be used to describe continuous data c. It is affected by skewness of data d. It is influenced by outliers 23. The error that results when a researcher fails to reject a null hypothesis that is false is :- a. Type-lerror b. Type-ll error c. Standard error d. Sampling error

17. b. Case-control<br />Explanation: A case-control study is the best design to establish risk factors for a rare disease because it starts with the outcome (the disease) and looks back to find exposures or risk factors.<br /><br />18. d. Cross sectional study design<br />Explanation: The most basic epidemiological study design is the cross-sectional study design. It involves observing a sample of the population at one point in time to assess the prevalence of a particular outcome or characteristic.<br /><br />19. c. Migration, mortality and fertility<br />Explanation: The major determinants of demography are migration, mortality, and fertility. These factors influence the size, structure, and distribution of populations over time.<br /><br />20. c. Adjusted rates<br />Explanation: Adjusted rates are rates computed by eliminating the effect of differences such as age distributions in the populations being studied. They provide a more accurate comparison between groups by accounting for confounding variables.<br /><br />21. b. Has no meaningful zero point<br />Explanation: The main difference between interval and ratio measurement scales is that an interval scale has no meaningful zero point. In an interval scale, the distance between values is meaningful, but the zero point is arbitrary and does not indicate the absence of the quantity being measured.<br /><br />22. b. It should not be used to describe continuous data<br />Explanation: The mode should not be used to describe continuous data because it only represents the most frequently occurring value in a dataset. Continuous data can have an infinite number of possible values, making the mode an inappropriate measure of central tendency for such data.<br /><br />23. b. Type-II error<br />Explanation: The error that results when a researcher fails to reject a null hypothesis that is false is a Type-II error. It occurs when the null hypothesis is incorrectly accepted, leading to a false negative conclusion.