Thursday, June 19, 2014

Weighted -- to national norms?

Female college students are more concerned about sexual violence on campus than are male students and are less likely to think their colleges and universities are doing enough about it, says a survey. While you collect yourself and yell "duh" at the screen, here's the part of the survey I find interesting.
The survey was conducted over three days last week, with 1,765 students taking the poll. The respondents were a mix of college and college-bound high school students who are members of Chegg's Chegghead panel, a group of more than 15,000 students who are invited to respond to Chegg surveys. The data were weighted to reflect national norms.
National norms? I don't think that word means what you think it means. 
Normally we weight data to reflect demographics (age, sex, etc.) of a population we're trying to describe. Simply put, if your sample is light on females compared to Census or other data for a population, you'd weight male answers a little less, female answers a little more. Norms? Imprecise wording. A "norm" is a standard or acceptable behavior, unless by some chance they mean the mathematical definition of "norm," which is "the product of a complex number and its conjugate, equal to the sum of the squares of its real and imaginary components, or the positive square root of this sum." I'm willing to bet it's not the mathy one. Plus this is at best a convenience sample of "Cheggheads," so we have no way of knowing how representative it truly is of all college students.

Thanks to David Simpson for pointing this one out to me.

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