Gratifying that the right data can change minds.  Midway through the last session, I asked whether parasitic worms could impair the cognitive performance of children – after I had explained basic worm biology and the pre-1930s correlational data supporting the idea (the polls may take time to load):

Then I went through the modern correlational and then experimental evidence, including the experimental on rodents and the beautiful double blind placebo trial of Nokes et al. with kids from Jamaica.  And then polled the class again.

So evidently most were persuaded.  We’ll see what happens when we get into something more contentious. Experience tells me you can use a correlation to persuade anyone of anything – if it fits their prejudices.