Question

Starbucks wants to survey its employees regarding employee satisfaction in Chicago. It divides the city into 15 geographic regions and selects a simple random sample from each region. What kind of sample is this?

	A.	A cluster sample.
	B.	A stratified sample.
	C.	A simple random sample.
	D.	A systematic sample.

A researcher studies two groups of subjects. One group consists entirely of women, the other entirely of men. He measures and compares their resting heart rate, recorded in beats per minute.  Which of the following is true? Select one.

	A.	The explanatory variable is gender.  Resting heart rate is a categorical variable.
	B.	The explanatory variable is resting heart rate .  Resting heart rate is a categorical variable.
	C.	The explanatory variable is resting heart rate .  Resting heart rate is a quantitative variable.
	D.	The explanatory variable is gender.  Resting heart rate is a quantitative variable.

Answer 1

The Options given in the question and their meanings are as follows.

A) A cluster sample is when the population is divided into separate groups or clusters and then a simple random sampling of the clusters is done.

B) A stratified sampling is one where the population is divided into separate groups and then a simple random sampling from each group is done.

C) A simple random sampling, takes samples from the entire population without looking at groupings or sub groupings.

D) A systematic sampling is one where a sample is selected based on a certain criteria. for eg every 3rd name in the directory etc.

From the above we see that the correct answer is OPTION B: Stratified Sampling.

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There are 2 important factors here. Gender - Male or Female. Therea are no numbers attached to them, hence they are numerical or quantitative. Therefore they are qualitative (as we discern a quality) or Categorical (as we can classify them into 2 categories).

Resting heart rate, is a value that we get. Hence it is numerical, and therefore quantitative.

The resting heart rate tells us a certain value (the rate of the heart beat), which can be explained if it is a male or female. Therefore the resting heart rate is an explanatory or dependent variable (for ed. because the resting heart rate is X, therefore it must be a female).

Therefore OPTION C: The explanatory Variable is resting heart rate. Resting heart rate is a quantitative variable.

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