Chapter 13, Problem 3E

a)

To determine

To explain the type of study.

Answer to Problem 3E

This study is Retrospective observational study.

Explanation of Solution

First need to understand about the experimental study and observational study:

Experimental study: Assigning people or things to groups and applying some treatment to one group, while the other group does not receive the treatment.

Observation study: In an observational study, measure or survey members of a sample without trying to affect them.

There are types of Observational study:

Retrospective: The data are collected from the past by going back in time.

Prospective: The data are collected in the future.

Cross-sectional study: In this type, the data are collecting at one point in time.

This study is Retrospective observational study as the data collected from the past and not treatment is imposed on the subjects.

b)

To determine

To explain whether the choice is appropriate to investigate this problem.

Answer to Problem 3E

Yes.

Explanation of Solution

It is an appropriate choice to investigate this problem. There might be some people who have not MS. Therefore, there would be a better choice to carry out a study with retrospective observational study than other study.

c)

To determine

To find the subjects in the study.

Answer to Problem 3E

The subjects are U.S. military personnel.

Explanation of Solution

The subjects given the information about the MS and do not have MS. Therefore, the subject is U.S. military personnel.

d)

To determine

To find the variables in the study.

Answer to Problem 3E

The variables are Vitamin D level and Developed MS.

Explanation of Solution

There is investigation regarding Vitamin D and developed MS. Hence, the variables are Vitamin D level and Developed MS.