Bias by Design - By the Numbers
Most of the numbers made sense to me. The number of libraries that held a particular title; number of titles reviewed; the total number of titles in the survey. When I got to the final set of tables, I was flummoxed. There were little boxes titled "Mean=" And in those boxes, after the mathematical operator (or equal sign) there were numbers: bigger numbers and smaller numbers. It took me forever to figure out what those numbers really meant. In fact, it wasn't until this morning that I had an epiphany and all became clear. For those of you who are math geeks and understood what they signified: stop rolling your eyes and shut up. I'm willing to bet that Stephen Hawking was quite proud of me when I managed to get 4 pages into A Brief History of Time , 20 pages into A Briefer History of Time , and nearly a quarter of the way through The Universe in a Nutshell . However feel free to correct any of my assumptions or mathematical errors. Just be nice - I can find out where you live and I'll have your mom cut off the power to the basement. At first glance those numbers are potentially damning. Take a look at the last few columns. Total Mean for favorable books is 214. The same for unfavorable books is 633. Which leads Tomeboy to his conclusion that for every 3 libraries that have a title critical of ID there is 1 that has title that is supportive. [NOPE (Note Of Personal Embarrassment) - when I saw that number I jumped all over it. AHA! If you add the mean for the top 21 unfavorable titles (389) to the mean for what I thought was the bottom 18 titles (214) you end up with a total of 593 and a rough proportion of 1 to 1. The condensed version of Tomeboy's response was: "Nice try, but no go". Evidently the phrase "Total" in "Total Mean" meant just that. It was the total mean for all 39 titles. Who knew?] However, I was left with an even more perplexing paradox. If you compare the means for the top 21 unfavorable titles (633) with the top 21 favorable titles (389) you end up with a proportion of 1.63 to 1. Using Tomeboy's analysis, and being generous, that would mean 2 libraries having an unfavorable title to every library that has a favorable title. That is where I got confused. When you add in the bottom 18 favorable titles, you end up with a proportion of 3 to 1. If libraries had stopped at acquiring the top 21 titles, the chances for finding a library that carried a pro-ID book were better? The more titles you bought that support the idea of ID the less chance you were going to find a library that carried one? WTF? That's when I finally got smart and started to look at what was being measured. The numbers provided by Tomeboy measure the average number of libraries that buy a particular book in the three categories (Balanced, Not Favorable, Favorable). Comparing those numbers means that rather than comparing the number of libraries that have a unfavorable book to the number of libraries that possess a favorable book, Tomeboy is comparing the proportion of the average number of libraries that own a particular title - unfavorable to favorable. I don't know what that number means, or of what the importance of it is. [Math geeks: now would be a good time to jump in]. If you want to compare the number of libraries that have unfavorable titles to the number of libraries that have favorable titles, just look at the raw numbers: Unfavorable: 13,298; favorable: 8236. No, I didn't double check my addition. Feel free. Which leaves us with an average of 1.61 libraries with a title that "pooh-pooh" ID to 1 library with a title that supports ID. At least our mythical patron's search isn't quite as onerous.