You are correct in saying that we must be cautious about sampling bias in research. However, the studies I mentioned are much more relaible than self-measured, self-reported surveys.
I was merely trying to re-calibrate contortionist's estimate of 100,000 to the much more realistic 600.
I might add that where men are volunteering to be measured or agreeing to be measured then I would expect the mean to be higher since guys with smaller erections are more likely to refuse.
Here are the 3 studies I referred to:
Schonfeld and Beebe, published in the USA in 1942, found the median length for the group of 20-25 year olds was 13.02 cm. or 5.12 in. This is extremely close to the 12.89 cm. or 5.07 in. erect penis average produced a careful modern study (Wessells, Lue, & McAninch, 1996) in which doctors actually measured the erections of 80 grown men. AND, in the recent Italian study of 3,300 soldiers age 17-19, Ponchietti and his colleagues found the average stretched penis length (remember this is very close in length to the erect penis) to be 12.5 cm. or 4.92 in.
Penile length and circumference: a study on 3,300 young Italian males.
Ponchietti R, Mondaini N, Bonafe M, Di Loro F, Biscioni S, Masieri L.
Department of Urology, University of Florence, Italy.
OBJECTIVE: The knowledge of normal variations in the size of male external genitalia is of considerable interest to several disciplines. We carried out an extensive study in young Italian males to provide estimates of normal variations of penile dimensions. METHODS: The penile length in flaccid and stretched states and the penile circumference were measured in a random group of 3,300 young men aged 17-19 years and free from endocrine disorders and from congenital or acquired abnormalities of the penis. In a random sample of 325 subjects of the same set of people, penile length and circumference were also correlated with weight and height. Statistical analysis was performed with the Spearman test, because our data were not normally distributed as tested by the Kolmogorov-Smirnov test (p < 0.01). RESULTS: The median values of penile dimensions recorded in the present study are flaccid length 9.0 cm, flaccid circumference, at the middle of the shaft, 10.0 cm, and stretched length 12.5 cm. [4.92 inches] We also observed that the penile dimensions are highly correlated with height and weight. CONCLUSIONS: Since penile length and circumference correlate with anthropometric parameters such as weight and height, we suggest to consider themselves as two bodily measures which display a wide extent of normal variability along the general population.
Penile length in the flaccid and erect states: guidelines for penile augmentation.
Wessells H, Lue TF, McAninch JW.
Department of Urology, University of California School of Medicine, San Francisco, USA.
PURPOSE: We provide guidelines of penile length and circumference to assist in counselling patients considering penile augmentation. MATERIALS AND METHODS: We prospectively measured flaccid and erect penile dimensions in 80 physically normal men before and after pharmacological erection. RESULTS: Mean flaccid length was 8.8 cm., stretched length 12.4 cm. [4.88 inches] and erect length 12.9 cm. [5.08 inches] Neither patient age nor size of the flaccid penis accurately predicted erectile length. Stretched length most closely correlated with erect length. CONCLUSIONS: Only men with a flaccid length of less than 4 cm., or a stretched or erect length of less than 7.5 cm. should be considered candidates for penile lengthening.
There is not a great deal of point in trying to give averages for each teenage year as guys are at different stages of puberty. The variation from shortest to longest is too wide to make an average length a logical measure.
We can say though, from the three studies above where a doctor measured the penis and not self- report surveys, that the average erection length is 5.1 inches (14cms) and roughly two-thirds of men will have erections between 4 and 6.2 inches (10 and 15.7cms). 16% will have erections smaller than 4 inches. 97.5% of men will have erections less than 7.3 inches (18.5cms). Therefore five men in 200 will have erections of 7.3 inches or more. One man in a thousand will have an erection of 8.4 inches (22cms) or longer and one man in 10,000 will have an erection of 9 inches or longer (22.9cms). For every million men in the population there will be a hundred erect penises of 9 inches or more.
btw your calculations sounds good to me and more realistic too!
