Stratified Sampling The owner of a private food store is conce...

Question

Stratified Sampling The owner of a private food store is concerned about employee morale. She decides to survey the managers and hourly employees to see if she can learn about work environment and job satisfaction. From the list of workers at the store, obtain a stratified sample of two managers and four hourly employees to survey.

Table listing managers and hourly employees with names for selecting a stratified sample of two managers and four employees.

Accepted Answer

Mhm. Hi there. Welcome back, everybody. The next problem says, a university researcher wants a stratified sample from the list of employees at a campus library to survey job satisfaction. The staff list contains librarians and student workers. Obtain a stratified sample consisting of 3 librarians and 8 student workers. Describe how to select this sample from the staff list. So, here we need to start with what do we mean by stratified sample. And that means that we pick first subdivide our whole population into groups with a shared characteristic. And then once you've divided the sample, you randomly sample from each group. So rather than taking random individuals from the whole population, you have this subdivision first. And the benefit of this type of sampling is that you ensure that you have a truly representative set of samples, particularly when it comes to the smaller um group within the whole. Or what we might call smaller subgroups. So, this might indicate, it's not sure, but since our stratified sample should have 3 librarians and 8 student workers, it's likely that there are far fewer librarians in the whole staff population. And therefore, if we just picked randomly among the entire staff, um, we'd be less likely to have a representative sample of the smaller group librarians. So, which of our answer choices represents getting a stratified sample? So first, we would need to divide the staff list into librarians and student workers. And so that would be choice A, label librarians and student workers. So there's our uh subdividing. And then, once we label them, so like numbered, for instance, you randomly select 3 librarians from their labels, and 8 student workers from their labels, and then match the labels back to names. So, I'd take my group of librarians, numbered, use a random number generator to pick 3, then that's my batch of librarians, and the same thing with the students. So, in our other examples, we don't divide by shared characteristics. So, choice B says randomly pick 11 names from the entire list. So, this is not a stratified sample, since you're not subdividing the group. And the same with choice D, where it says choose the top 11 names alphabetically from the list without randomization. In addition, we might not hit any librarians at all. You could get all of, uh, you know, 11 of uh student workers there. And then, choice C, we're dividing the group, but not by a shared characteristic, it just divide the list into groups of 5 and pick every fifth person. So it's not, this is not going to be as representative of the group, especially when it comes to representing the smaller population. So that's why Cho C is not our answer. So, once again, we're looking for a researcher who wants a stratified sample from a list of employees at a campus library. The staff list has librarians as student workers, and we're told to obtain a stratified sample, consisting of 3 librarians and 8 student workers. How would you select this sample? And only 1 of our answer choices has the proper definition of a stratified sample, and that's choice A, label librarians and student workers. Then randomly select 3 librarians from their labels and 8 student workers from their labels, and match labels back to names. See you in the next video.

Key Concepts

Stratified Sampling

Sampling Frame

Sample Size Determination

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