Take Home Project/Test

A variety of popular health books suggest that the readers assess their health, at least in part, by estimating their percentage of body fat. In Bailey (1994), for instance, the reader can estimate body fat from tables using their age and various skin-fold measurements obtained by using a caliper. Other texts give predictive equations for body fat using body circumference measurements (e.g. abdominal circumference) and/or skin-fold measurements, but those measurements are highly unreliable (i.e., measurements tend to vary a lot when repeated on the same person).

Accurate measurement of body fat is inconvenient (e.g., a person must be completely submerged in water) or costly (laboratory analysis of biopsy samples). It is desirable to have easy methods of estimating body fat that are neither inconvenient nor costly and which produce reliable estimates.



Your company has been hired by a chain of health food stores to devise a way for store emplyees to estimate customer’s percentage of body fat. Your company has data on 252 people that were collected for a prior contract. [Note 1] Your boss insists that you use this data because it will save them a considerable amount of money and they will therefore make that much more money on this contract.

The variables on which measurements were taken in that prior study are:


Percent body fat using Siri's (1956) method


Age (years)


Weight (lbs)


Height (inches)


Neck circumference (cm)


Chest circumference (cm)


Abdomen circumference (cm)


Hip circumference (cm)


Thigh circumference (cm)


Knee circumference (cm)


Ankle circumference (cm)


Biceps (extended) circumference (cm)


Forearm circumference (cm)


Wrist circumference (cm)

Siri’s method of estimating a person's percent body fat produces accurate estimates, but it involves measurements that are not possible in a food store (e.g., it measures a person’s body density by completely immersing him or her in water).



Your task has three parts:

  1. Devise a formula for estimating percentage body fat as accurately as possible, using measurements easily taken by a store employee.

    The food store home office will then hire a company to program that formula into calculators. Store employees will then enter the various measurements, taken in the store, into a calculator. The calculator will then display an estimate of the person’s (estimated) percentage body fat.

  2. Write a report of your investigation for the store chain. Tell them
    1. The problem you solved for them
    2. What you did to solve it
    3. Your solution
    4. Your opinion about the accuracy of estimates that are produced by your formula
  3. Write a brief addendum (two or three paragraphs), for your company's eyes only, saying what you have learned that might be of value in future projects.


Hand in:

  1. Your report to the company (as outlined in #2, above)
  2. Your addendum to your company (as described in #3, above).

You may hand in your report by copying it to your take-home disk (and giving us the disk) or you may print it, handing us a hard copy of it.

Due Date: Monday, November 29, 1999, beginning of class.



Call me me or email me if you have problems. I will be traveling, so use only email or the number I've given here. Happy Thanksgiving!



I swear that I have done all work on this project without assistance, consultation, or collaboration from anyone other than Dr. Thompson, Mr. Trudell, or Mr. Saldanha.



Note 1: The data were generously supplied by Dr. A. Garth Fisher who gave permission to freely distribute the data for non-commercial purposes.