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Women "Advertise" Fertility

Posted by kdawson on from the but-we-knew-this dept.

Dik Zak writes with word of a paper published in the journal Hormones and Behavior. A study found that women take greater care over their appearance when they are at peak levels of monthly fertility. The researchers took two photos of each of 30 women, one near ovulation and one at the other end of her cycle. They then showed the paired photos (with faces obscured) to a group of observers, who were asked to judge in which photo the women were trying to look more attractive. The observers chose the "high fertility" subject nearly 60% more of the time than would be expected by chance.

4 of 317 comments (clear)

  1. No, 60% more by Chris+Burke · · Score: 5, Informative

    Not 60% of the time, but 60% more than expected if it were chance alone. So more likely 1.6 * (30*.5) = 24/30, not 18/30.

    But of course the actual number isn't in the article.

    --

    The enemies of Democracy are
    1. Re:No, 60% more by Surt · · Score: 5, Informative

      30 is a low sample size, but would not be unusual in psychology studies. There are statistical tests you can perform to find out the minimum effect size to declare significance. I've seen studies with meaningful results in as few as 8 samples.

      Nevertheless, this particular study had 1260 samples. 42 guessers * 30 guesses each. More than a thousand samples is plenty for significance.

      --
      "Who is the Journal of Quantum Physics going to believe?" --Stephen Hawking
  2. Re:60% of 30? by Surt · · Score: 5, Informative

    The article and summary are in disagreement. Choosing to assume the article is more likely to be right, it is 60% right guesses vs expected 50% right guesses.

    However, also omitted from the summary is 42 guessers guessing on the 30 dress-up-women in the study. That's 42x30 guesses, with a 60% correct guess rate overall. 60% with more than a thousand sample points is well within the usual scientific standard for statistically significant.

    --
    "Who is the Journal of Quantum Physics going to believe?" --Stephen Hawking
  3. About Statistical Significance by flynt · · Score: 5, Informative

    I am a statistician, and reading through the comments hear, am saddened that many readers claim that "statistical significance" could not have been achieved in this study because of a sample size of 30 women. First, that's only part of the random sample in this study, the other part is men sampled to judge the pictures.

    Second of all, I have looked up the actual publication in "Hormones and Behavior", and the p-value associated with their main test is .01, which usually signifies statistical significance.

    Ultimately, determining whether some difference in populations is due to chance depends on more than just sample size. It depends on how large of a difference you want to detect, and the variance of the measurements within a group. Of course, larger sample sizes help, but it ultimately depends on what you're studying, and the design of the experiment.

    So while I definitely applaud being sceptical of all statistics, I urge you to look up the actual publications, read the methodology, and then decide if the results are something you believe. Kneejerk reactions to n = 30 don't really help anyone though.

    I have not read through this publication in its entirety yet.