Oct

16

Sleeping Dogo Argentino (big white dog)
The other day I wrote about how I had never had the need to do a binomial test for a proportion with SAS. In my business, at least, the question of whether the proportion in the population equals X just doesn’t come up very often. Actually, given that I had taught not one, but two courses on non-parametric statistics in the past and then forgotten about them, it is possible that I did actually do such a test in the past and forgot about it.

I was trying to think about a real-life useful application for this test and it being election season and all, this occurred to me…

Let’s say your candidate, Bill W, is running for dogcatcher. A poll of nearly 2,500 people shows him to have 48% of the vote. Does he have a chance in hell of winning this election?

The question you want answered is whether or not 50.1% is within the realm of probability (the 95% confidence interval) .

As a reminder, the SAS code is

proc freq data = dsname ;
tables candvote / binomial (exact  equiv p = .501) alpha = .05 ;

SAS will test for the proportion for the FIRST level in the frequency table, but I’m assuming they are in alphabetical order and Bill comes first.

Table shows 50.1% is not in 95% CI but > 50% is

You can see two things from these results. First, your buddy Bill W does not have a chance of getting 50.1% of the vote. However, it is within the 95% confidence interval that he could get 50.02% of the vote.

Still, if I was you, I would be looking for a different job. Maybe as campaign manager for his opponent.

I had a lot more I had to say about categorical data analysis but I did not have time to put it all in one post and I already have seven draft posts that I started and didn’t finish.
Tomorrow we will look at one possible use of the McNemar test – to assess the plausibility of my personal opinion that the claim that teaching about the contributions of famous gay people to science and literature, or anti-bullying classes makes children decide that,

“Hey, I thought I was straight, but on second thought, now I want to have sex with Bob!”

is total bullshit.


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