## Chapter 71. Statistics

Which of the following is the outcome variable for a study?

a. Dependent variable

b. Independent variable

c. Confounder

d. Population

Answer a is correct. There are three types of variables: dependent (DV), independent (IV), and confounding. The DV is the response or outcome variable for a study.

Answers b and c are incorrect. The IV is a variable that is manipulated and a confounding variable is any variable that has an effect on the DV over and above the effect of the IV, but is not of specific research interest.

Answer d is incorrect. A population refers to all objects of a similar type in the universe, while a sample is a fraction of the population chosen to be representative of the specific population of interest. Thus, samples are chosen to make generalizations about the population of interest.

Which of the following represent scales of measurement? Select all that apply.

a. Nominal

b. Ordinal

c. Interval

d. Ratio

Answers a, b, c, and d are correct. There are four levels of measurement: nominal, ordinal, interval, and ratio scales. The scale of measurement is an important consideration when determining the appropriate statistical test to answer the research question and hypothesis.

A pharmacy resident in South Carolina is charged with evaluating daptomycin as her research project for the year. She is evaluating all patients within 18 months and comparing them to vancomycin. The primary outcome is clinical response as defined by clearance of bacteremia within 5 days. Her data collection sheet has two boxes for the primary outcome (yes and no). What type of measurement scale is the resident collecting?

a. Nominal

b. Ordinal

c. Interval

d. Ratio

Answer a is correct. A nominal scale consists of categories that have no implied rank or order (male vs female; or absence vs presence). The patient can fit into only one category; that is, the data points are mutually exclusive.

Answers b, c, and d are incorrect. An ordinal scale has all of the characteristics of a nominal variable; however, the data are placed into rank-ordered categories. Interval scales increase the information provided by an ordinal scale by allowing researchers to quantify a meaningful ...

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