The tutor estimates the standard deviation of holiday weight gain.

I hoped to lose weight over the holiday season; alas, I gained a pound. Searching the internet for opinions about it, I came upon this surprising article, which suggests that the average weight gain over the holiday season is perhaps less than a pound.

Let’s be safe and call the mean gain exactly a pound. A mean, without a standard deviation, is of limited use. (μ=mean, σ=standard deviation) However, we can estimate σ by another claim of the article – its estimate that less than 10% of people experience weight gain 5lbs or more over the holidays.

According to the normal distribution table, 90% of the distribution is less than μ+1.28σ. With the estimate μ=1lb, this implies 1+1.28σ=5→1.28σ=4→σ=4/1.28=3.125lbs. Apparently, the average holiday weight gain could be 1lb, with standard deviation 3.125lbs.

I’ll be commenting on implications of this estimate in a coming post. In the meantime, let’s keep working off that holiday gain:)

Source:

Harnett, Donald L. and James L. Murphy. Statistical Analysis for Business and
   Economics. Don Mills: Addison-Wesley, 1993.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.