Research Methods

Body Mass Index Homework

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NOTE: This page is meant to be printed out for your convenience when you work on your homework. It does not contain the links to other sites; you can get the complete information on the Research Methods syllabus.

In this assignment, we will assess whether the Body Mass Index relate to our perceptions of the health of our lifestyle? In this exercise, we will look at the relationship between a couple of different health-related measures. For this exercise, we will collect data in class; I will add the data you provide to an existing set of data called bmi that you can access on the Nova server. Specifically, we will use the notion of the Body Mass Index developed, in part, by Dr. C. Everett Koop, former Surgeon General of the United States.

To access the data, follow these steps: Q Drive (Nova) --> Faculty--> Beins --> PS308BB --> DATA --> bmi

A useful background article that you can get online from the Ithaca College library is Calle, E. E., Thun M. J., Petrelli, J. M., Rodriguez, C., Heath, & C. W. (1999). Body-mass index and mortality in a prospective cohort of U.S. adults. The New England Journal of Medicine, 341, 1097-1105.

What do the data say?

When you go to the Library website, you should select Biology in the box where it says Research by Subject. Then choose Biological Abstracts. If you do a search for Calle in Author, New England Journal of Medicine in Source, and Body-Mass Index in Title, you will get a link to the article.

You can get a summary of some relevant research from a British report. In this research, investigators asked participants to give self-report data on their health and on their lifestyles. You don't need to read the entire report, but you can extract some material useful for this assignment. There is also other research that suggests that overweight people are not at greater risk. What should you believe?

The question you will address is whether there is a relationship between the lifestyle ratings that students provided and their BMI measurements.

Purpose of the Homework: This assignment will provide you with additional practice using SPSS and writing descriptions and explanations based on data.

Objectives for the BMI homework:

• Learning to open and work with data files in SPSS
• Completing simple data analyses
• Drawing conclusions based on data
• Recognizing the limitations of research methodology and data
• Structuring method, results, discussion and reference sections in APA style. (You do not need an abstract or introduction.)

What you need to do to complete the BMI homework successfully: In this assignment, you will use SPSS to conduct a simple data analysis, then you will interpret the data and draw a conclusion. In addition, you will need to identify the limitations in the methodology we used to draw our conclusions. No methodology is perfect, so you have to identify what your methodology helps you to understand and how your methodology limits your conclusions.

In class, you will generate two hypotheses related to a person's BMI (which correlates with risk of disease)

• Is BMI related to a person's self-report of the healthfulness of a the lifestyle. What is the logic behind your hypothesis?
• Do BMIs of women and men differ reliably?

Describe the results of our study:

• Identify the correct statistical tests for the two hypotheses (2 pst.)
• Conduct the tests using SPSS and describe the output: Are the results significant?(4 pts.)
• Describe the results in normal, everyday English. Do NOT use statistics terminology here; just say what happened in words that a normal person could understand. In your description, do not come up with an explanation of why you think the data occurred as they did. Just tell what happened.

Say what you think the data mean:

• Draw conclusions based on the data and on previous research. That is, why do you think the results occurred the way they did? Make sure you discuss the results for both statistical analyses that you did. (4 pts)
• If the relationship between BMI and ratings of lifestyle is significant, explain what this tells you. If there is no relation between BMI scores and ratings, try to explain why this is so. The research on the BMI shows that it predicts health and mortality. If the correlation is not significant, why wouldn't student ratings of healthfulness of lifestyle relate to BMI, which is related to healthfulness?(4 pts)
• If women and men have different BMI scores, on average, explain why this might be so? (3 pts)
• What are the problems with our methodology? That is, what about our methodology limits the confidence you have in your conclusion? How could you improve the methodology to eliminate the problems you spotted? (3 pts.)

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Modified January 7, 2008