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Abstract
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| A
Related Study
The following article was published after I had collected data,
but before my article appeared in print.
H. Wessells, T. F. Lue, & J. W. McAninch: Penile length in the
flaccid and erect states: Guidelines for penile augmentation. J.
Urol., 156: 995-997, 1996.
This research used as subjects 80 physically normal men who were
evaluated for erectile dysfunction. Each man had his penis measured
with a tape while flaccid, while flaccid but stretched, and while
erect following an intracavernous injection of the vasodilator prostaglandin
E1. Of the subjects, 20% were black, 12.5% were Asian, and the remainder
were white. The men ranged in age from 21 to 82 years old with a
large cluster in their 30s and another in their 60s. The average
age was 54.
This study found the average flaccid length to be 3.47 in. with
a range from 1.97 to 6.10 in. Stretched length was very similar
to erect length. And the average erect length was 5.07 in. with
a range of 2.95 to 7.48 in.
The Wessells study appears to provide a cautionary note regarding
the average values for length found in the photo sample (6.05 in.)
and the Kinsey self-reported sample (6.20 in.) Before comparing
these three studies we must acknowledge that subjects were selected
to be in the Wessells study because they presented themselves at
a urology clinic with erectile problems. It is possible that this,
in itself, caused those men to be systematically different in penile
length from the men in the main article reported in this site. However,
this conclusion seems unwarranted since there are no theoretical
reasons or published reports suggesting that individuals with erectile
dysfunction might be different in penile length from the general
population. The almost 14-year difference in average age between
the samples also might be a source of difference in average penile
length, yet based on Kinsey data, variation from age 20 to age 60
should account for a decrease of no more than .4 in.
So, if attendance at a urology clinic or slightly older average
age is an insufficient basis for explaining the whopping 1-inch
difference in the means produced by these studies, what is? I would
nominate as the culprit the fact that the photo research and Kinsey
subjects self-selected themselves to participate in a sex research
study. In other words, these samples were more likely to include
a greater proportion of men who were not only willing but anxious
to be studied - who had some degree of pride in their own prowess
and anatomy. To this, add the fact that the Kinsey subjects mailed
in their own penile measurements taken by themselves in the privacy
of their homes. If there was any tendency, conscious or unconscious,
to exaggerate the measurements, full opportunity was there.
I conclude that self-selection bias in the photo research sample
and self-selection plus self-reporting bias in the Kinsey sample
have caused these samples to produce a mean for erect penile length
that is too high to be a good estimate of length for the general
male population. While it is impossible to know if the Wessells
sample of urology patients provides any better estimate for the
general population mean, I am prepared to believe it does. I believe
this because the subjects did not select themselves specifically
or solely to take part in the study, but rather where recruited
when they attended a urology clinic.
At this point, research has not produced a reliable estimate of
average penile length for the general population of all men. The
Wessells research feeds our suspicion that the mean, when it is
finally measured, will be lower that the values determined in the
article: Penile erections: Shape, angle, and length. In that
eventual research the key methodological hurdle will be to draw
a sample that will adequately reflect the general population of
men.
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