Friday, October 2, 2015

Selection Bias - Erich

Sometimes when I teach statistics, I ask my students to look at the website and I ask them to decide if this website is biased or not. The purpose of the site is to discuss high fructose corn syrup and whether or not it is the same to your body as sugar. The articles listed there are well founded scientific studies. But with a click on the About link, you learn that this website is posted and maintained by the Corn Refiners Association. Hmm, sounds like there might be a vested financial interest, right? But the articles are so science-y!

I'm teaching my students about selection bias. Yes, these are all great articles. But the Corn Refiners Association has decided only to include articles that say high fructose corn syrup is no different than sugar as far as your digestion is concerned. They are selecting those articles and purposefully not selecting the equally well written scientific studies that do find a difference. That's a selection bias.

But even knowing about selection biases, it is easy to fall into them oneself. Case in point: Syarra just celebrated her ninth birthday. And I was discussing with her how her year as a eight year old went. I talked about how she was caring, how she worked hard to learn things, how helpful she was, and how much fun it had been to be with her. I decided she had a great eighth year.

At that juncture, Carver pointed out to me that I had a selection bias. I was only listing the many good things Syarra had done and ignoring any time she had been less than ideal. He's exactly right. But in this instance, as a father, I think my selection bias is only natural and good.

Well, let me tell you about some amazing firsts. And you should know I have a selection bias.

I inhaled air in Africa for the first time. (It's actually surprisingly similar to inhaling anywhere else.) I rode on a sleeper train in Africa for the first time. It's actually the first time I ever rode a sleeper train anywhere. But the “in Africa” adds a new element of flair. I bought groceries in Africa for the first time. I saw Johannesburg and Cape Town for the first time. I had a pocket full of rands (which is the currency here, not a euphemism for posies) for the first time.

Of course there were less pleasant firsts (like suffering from jet lag in Africa for the first time) and there were more confusing firsts (like trying to figure out how to use one's tickets to take the Gautrain in Johannesburg.) But I am focusing on the cool firsts and laying my bias bare.

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