Question

In each of the following scenarios,
i. Identify whether the data are paired or independent.
ii. Consider whether a design that produces the “other type” of two-sample data might be preferable (for example, if the data are paired, consider whether a design that produces
independent data might be preferable). If so, briefly describe the alternative study design. If not, briefly explain why the design presented in the question statement is preferable.

For each scenario, limit your description/explanation to at most five sentences.

a) Does salary differ by gender for full professors at American universities? Draw a random sample of 50 female full professors and 50 male full professors, and compare their salaries.
b) Does Vitamin E increase artery thickness? Measure artery thickness for a group of patients before they start taking Vitamin E regularly for two years. Compare initial artery thickness to artery thickness at the end of the study.
c) Is a Mediterranean diet effective for weight loss? Compare the weights of individuals before and after going on the diet regimen.
d) Do Intel’s stock and Southwest Airlines’ stock have similar rates of return? Take a random sample of 60 days, and compare Intel’s and Southwest’s stock on those days.

Answer 1

(a)

(i)

The data are independent.

(ii)

Gender of a full professor is either male or feamle. So, paired type of data can not be collected in such situation.

(b)

(i)

The data are paired.

(ii)

Collection of paired data for the given situation is time consming (as long as two years here). So, using independent data would be helpful to reduce the complexity of data collection.

(c)

(i)

The data are paired.

(ii)

Using paired data is good enough as it nullifies the effect of difference in weight among individuals.

(d)

(i)

The data are paired.

(ii)

Using paired data is fine as stock size is highly dependent upon change of people's demand and purchase.