{"id":162,"date":"2015-03-06T01:06:33","date_gmt":"2015-03-06T06:06:33","guid":{"rendered":"http:\/\/www.datagoneodd.com\/blog\/?p=162"},"modified":"2015-03-06T01:29:15","modified_gmt":"2015-03-06T06:29:15","slug":"a-cut-too-deep-a-case-study-in-bias","status":"publish","type":"post","link":"http:\/\/www.datagoneodd.com\/blog\/2015\/03\/06\/a-cut-too-deep-a-case-study-in-bias\/","title":{"rendered":"A Cut Too Deep: A case study in bias"},"content":{"rendered":"

If I were to create Francis Walker’s Rules of Using Statistics, Rule #1 would probably be this:<\/p>\n

1. You are not allowed to use a statistic in an argument unless you have read the underlying research<\/em><\/p><\/blockquote>\n

This rule would also have a sub-part:<\/p>\n

1a.\u00a0Do not skip from the “Introduction” section to the “Results” section, you must also read the “Methods” section<\/em><\/p><\/blockquote>\n

In each of the posts I’ve written so far, bias has played a role, and by reading the “Methods” section of research you can get an understanding of what type of bias might be influencing a particular research study. \u00a0The other week I read an article on Ars Technica<\/a> that reminded me of the first time I realized just how critical the “Methods” section really was. \u00a0What was said Ars article about? Digital Security? Space Travel? General Technology, perhaps? \u00a0Nope – it was about circumcision<\/a>.<\/p>\n

While admittedly I have not done very much research on the subject, on balance it seems like whichever decision a parent makes, their son is probably going to turn out just fine. For some people though, the issue of circumcision is highly contentious. \u00a0In fact, I’ve often found it kind of amusing how passionate people can get about the subject and the Ars article reminded me of a comment thread I remembered reading years ago. \u00a0In that thread, one of the arguments used by an adamant anti-circumcision advocate was a somewhat strange sounding statistic – A US study on the matter had found that 6 out of 7 women preferred sex with men with an uncircumcised penis. \u00a0This struck me as odd. \u00a0Growing up in the US where many men are circumcised, I’d heard of women either not caring one way or the other, or preferring a circumcised penis as that is what they were used to. \u00a0I certainly never got the impression that there was an overwhelming preference for an uncircumcised penis. So I decided to read the underlying research.<\/p>\n

The study in question was\u00a0The effect of male circumcision on the sexual enjoyment of the female partner<\/a>\u00a0from the January 1999 edition of BJU International1<\/a><\/sup>. I found the article on the site I linked to and sure enough, there was the stat right at the top of the “Results” section.<\/p>\n

CIRP Note: The results of this survey are somewhat obscurely stated. This survey surveyed 138 women. Of that group 20 (14.5%) preferred non-intact circumcised sexual partners while 118 or (85.5%) preferred intact non-circumcised sexual partners. This means that about 6 out of 7 women preferred intact non-circumcised partners while about 1 out of seven preferred non-intact circumcised partners.<\/em><\/p><\/blockquote>\n

If true, that certainly seems like a pretty convincing argument against circumcision. There is a\u00a0slight<\/em> problem though. \u00a0Below is the first paragraph of the methods section, let’s see if you can figure out what might be distorting the results:<\/p>\n

Women having sexual experience with both circumcised and anatomically complete partners were recruited through classified advertisements in magazines and an announcement in an anti-circumcision newletter. Respondents to the advertisements were mailed a survey to complete and return, the comments then compiled and the responses analysed statistically. The survey is continuing and this article reports the preliminary results.<\/em><\/p><\/blockquote>\n

Did you catch that? \u00a0They recruited participants from an anti-circumcision newsletter 2<\/a><\/sup> and got survey results 3<\/a><\/sup> saying that women prefer an uncircumcised penis. \u00a0Funny how that works, huh? Now they do at least acknowledge this in the study and attempt to address the issue:<\/p>\n

While this study shows clearly that women prefer the surgically unaltered penis, it does have shortcomings. The respondents were not selected randomly and several were recruited using a newsletter of an anti-circumcision organization. However, when the responses from respondents gathered from the mailing list of the anti-circumcision organization were compared with those of the other respondents, there were no differences. This selection bias may be compensated to the degree that each respondent acted as her own control, using her subjective criteria on both types of penises. The findings cannot be completely attributed to selection bias.<\/em><\/p><\/blockquote>\n

My first reaction to this was,”Wait a minute, if the results from each pool of respondents were the same, that means that 15% of the women who subscribe to the anti-circumcision newsletter prefer sex involving a circumcised penis.” \u00a0A bit of a head scratcher there. \u00a0The authors also neglect to mention what portion of the respondents come from the anti-circumcision newsletter, what the the other magazines they advertised in were, or how they advertised the study. \u00a0In the absence of this information we are left to trust the they are unbiased and that these factors don’t affect the survey’s results. \u00a0So are the authors unbiased? \u00a0If you’ve read my earlier posts, you can probably guess what the answer to that question is.<\/p>\n

“Hold on,” you may be saying to yourself, “just how biased could someone be on the topic of circumcision?”\u00a0Oh just you wait.<\/p>\n

At this point, you may have noticed that the website I linked to had another note at the top of the study:<\/p>\n

CIRP note: The authors of this article have written a book entitled Sex As Nature Intended It<\/a>. The book has a website at www.sexasnatureintendedit.com<\/a>.<\/em><\/p><\/blockquote>\n

Oh boy 4<\/a><\/sup>.\u00a0I now direct your attention to Chapter 11:\u00a0Kristen O’Hara’s Personal Story<\/a>5<\/a><\/sup>. You should really read the whole thing, but allow me to provide you with a brief synopsis:<\/p>\n