A fictional case study by Gregory Taketa. For non-data Managers, this case illustrates that your analysts will not be able to solve anything as complicated as weight loss using typical linear regression methods. Regression practitioners can use a MS Excel Data Set to approach this problem by transforming the variables with respect to growth and time.
I’m sure you or somebody you know has an interest in a healthier diet or lifestyle (I’ve lost 25 lbs. in 19 months by the time of this writing).
A friend of mine has a fantastic web site for those of you who are interested in low-carb recipes:
This site has many visitors, and you gotta visit at least once just for the clever name!
As you know, weight lifting is very helpful for weight loss because an increase in muscle mass, all else equal, yields higher fat burn. This burn happens even when you are not actively exercising, so in the diet world, this is comparable to passive income!
The Case: Estimating the Impact of Weight-Lifting
Our subject weighs 200 lbs. at the start of a diet. At the end of each week, he marks his weight and whether he did a diligent amount of weight-lifting (according to his health advisor) that week. As typical of any binary (dummy) variable, “1” indicates “yes,” and a “0” indicates “no.”
Although many other variables, including calorie intake versus metabolic requirements, influence body weight, we will assume for simplicity that these variables have remained fixed.
Key Case Facts
- For the first 8 weeks, our subject has lifted weights but notices no weight loss.
- After the 8th week, he gives up on lifting weights (he perceived no weight loss earlier).
- He exhibits some weight loss from weeks 9-16. This is because his gain in muscle mass takes time, about 8 weeks in this case.* He does not know about this.
*Disclaimer: I am not a fitness expert of any sort, and this case is simplified for the purpose of quick practice. I do not have factual evidence and do not suggest that 8 weeks is required to develop muscle mass.
Did the weight-lifting help our subject lose weight? How could you demonstrate it? What was the rate of weight loss for the given effort?
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