### another historical day for psychologists

So how's it going sports fans?

It seems that I have been neglecting my blog a little bit lately. I know, I know . . . it seems like I get into a good rhythm for a couple days, and then BOOM!, I'll hit a dry spell and won't write anything new for weeks. Oh, the time graduate study takes from me. Well, I do have a decent excuse . . . I've been doing a lot of traveling. Firstly, I spent some time in Albuquerque, NM for the 9th annual meeting of the Society for Personality and Social Psychology. And secondly, I'm interviewing for Ph.D. programs. Fun stuff. Interestingly, before February, I have never flown on a plane before (I guess a live a sheltered life, ha). Yet I flew on 10 different flights in the past week and a half!

Well, besides leaving me tired, my traveling has left me with several posts that I plan to write up soon. The current post, on the other hand, is about an event that occurred on February 17th, 1890. Give up? It's the birth date of R. A. Fisher!

You might be asking yourself, who is R. A. Fisher and why is he important? I'll tell you. Sir Ronald Aylmer Fisher was a British statistician and evolutionary geneticist, and one of the founders of the modern evolutionary synthesis. He basically showed quantitatively that "inherited traits were consistent with Mendelian principles." As well, he built the foundation for modern statistical theory and population genetics. To say the least, he was a bright guy.

A lot of Fisher's work concerned the variation of inherited traits among plants, so why is he important to psychologists? Well, like I stated before, he practically fathered modern statistical theory. He created advanced techniques that we still use today and wrote influential books on research design and analysis, including his first book, Statistical Methods for Research Workers (of which I actually found a used early edition and got it for free!). Most importantly, especially for social psychologists, he invented the statistical technique referred to as "analysis of variance," or simply, "ANOVA."

To put it simply, ANOVA is a procedure that deals with the differences between groups (specifically, two or more groups), rather than just describe the relationship between variables. This makes it a considerable advancement from the statistical technique of correlation. In correlational research, you can't really make statements about cause and effect. Whereas, in experimental research using ANOVA's, you are given more insight to do so, which is why it has become the most popular (and often abused) statistical procedure in psychology . . . especially social psychology! ANOVA gives us it's extra insight by examining the ratio of the observed variability BETWEEN groups (what we can account for) and the observed variability WITHIN each group (uniqueness that we can't account for). Or in even simpler terms that my thesis adviser, John Nezlek, would say, an ANOVA is the ratio of "what we know" over "what we don't know."

Here's an example to make it a little easier to understand:

Let's say that I have a drug and I think it makes people more aggressive. So I draw two random samples of people and I give one sample a dose of the drug, while the other sample gets a placebo (sugar pill). Then I measure how aggressively (perhaps how many times each person physically harms another) each person in each sample acts. To say that my drug causes aggression, one would have to say that the variation in aggressive behavior between the two groups (drug group and placebo group) is much larger than the variation within each group (do all placebo participants act similar? do all drug participants act similar?). So if the the drug group does act more aggressively than the placebo group, and each member of the drug groups acts similarly aggressive, then it's likely that my drug causes aggression.

Well, that's my short and simple description of Analysis of Variance. I know that my meager post does not give Fisher's brilliance the full justice that it deserves, but I try. So, even though I'm just a little late (my time says 3:18 am on Feb. 18th) . . . HAPPY BIRTHDAY Ronald Fisher!

## No comments:

Post a Comment