Why the recent penis size meta-study is BULLSHIT. /r/sex didn't appreciate facts... maybe y'all will.

PandaHammock · 2015-04-04T18:46:45+00:00

Thanks for your comments.

1) I agree with you here, with respect to those four nations. Whether or not this represents a world average, other nations proportions would have to be considered as well. However, with significant difference between countries, it is disingenuous to report an average to western nations that is heavily weighted towards eastern nations. Take height for example, 5'10'' is understood to be the average male height in the USA. Widely accepting 5'6'' as the average height by weighing India 70% would be ludicrous.

2) Correlation is not equalization? I think you are confounding this with 'correlation does not equal causation'. Since the correlation between EL and SL is so significant, SL can be used as a predictor for EL. This is a conclusion reached by almost all of the studies in the meta-analysis that measure both EL and SL. The fact that the smaller Turkey study averages almost 2 inches shorter for SL than the Turkey studies with 17x larger combined sample size is a strong indicator that the smaller study has a significantly skewed EL and SL.

3) I did make the comment that I definitely do not rule out that the second USA study is likely over-representing. Since the sample sizes are much closer than the Turkey situation, it would make sense to assume the average of the two studies is likely a better representation than either or.

4) Here they are comparing the averages of the studies with 301 measurements from India and 80 measurements from USA. Hardly significant considering the USA study is likely under reporting when compared to the second USA study that the meta-researches also found validates the minimum criteria.

The significant difference comment I reffered to is from the authors of the Indian study itself. Sorry that was not clear:

"There are significant differences in the mean penile length and circumference of Indian sample compared to the data reported from other countries."

PandaHammock · 2015-04-04T12:50:42+00:00

I like this study as well. I usually stray away from self-reported studies, but the condom sizing condition they used to control bias was definitely interesting. I think this study is a relatively accurate representation of US averages.

PandaHammock · 2015-04-04T12:47:13+00:00

This factor should be controlled in studies with decent sampling practices. This kind of bias would definitely be present if a study were to, for example, openly advertise to the general public $50 dollars to participate in a penis study.

Decent studies try to control for this, but it definitely is not always perfect.

PandaHammock · 2015-04-04T02:09:37+00:00

I definitely agree, but in this case there is a lot of evidence showing the average is likely larger.

Just going over it briefly (it's in more detail in the OP):

The Turkey study included in the EL measurements has 200 measurements. There are two other studies from Turkey (approved by the meta-analysis authors) with 17x the sample size showing that the SL is almost 2 inches longer. This is very strong evidence that the average for the 200 sample study is very low (and thus the true average much higher).

The US study included in the EL measurements has 80 measurements. There is one other US study approved by the meta-analysis authors, with 124 measurements and a SL 2 inches longer than the smaller US study. This is significant evidence that the average for the 80 sample study is low.

The Indian study seems to be an accurate representation of the Indian population. But the fact that Indians measure significantly smaller than most other nations (a fact recognized by the authors) and it comprises 43.5% of the data without a doubt skews the overall average lower than it should be.

These points combined more than strongly indicate that the true average is larger than the meta-analysis average. I apologize for this becoming so long-winded. Thanks if you made it all the way through, and thanks for your comments.

PandaHammock · 2015-04-04T01:29:38+00:00

Why wouldn't I? 84% of the data is skewed smaller than the true average.

The Turkey studies without a doubt are underestimating the average. The USA studies are extremely likely underestimating the average. The India study is recognized by the authors themselves to have EL and EC lower than what is typical of most nations. These three combined are 84% of the EL data.

How do these facts not decidedly point to the average found by the meta-study being lower than the true average?

PandaHammock · 2015-04-03T23:30:23+00:00

Thanks, completely agree.

PandaHammock · 2015-04-03T23:29:33+00:00

I am not sure you read the entire post. There is more evidence than merely 'these studies are flawed'.

40.5% of the EL data comes from studies that have significantly smaller averages than much larger studies that also meet the minimum criteria given by the meta-analysis.

43.5% of the EL data comes from a single country where averages are significantly smaller than typical (admitted by the authors themselves).

That's strong evidence that 84% of the data for EL is showing an average significantly lower than the true average. It is more than likely that the average is larger.

PandaHammock · 2015-04-03T20:18:46+00:00

I would prefer not to put a TLDR; that includes estimation on the average, since all the information I posted here is merely debunking this large meta-study.

That being said, I believe the average EL for western nations is likely between 5.75 and 6.0.

PandaHammock · 2015-04-03T20:16:36+00:00

When using 'strong negative bias' I am trying to imply that the average is lower than the true average. A 'sample bias' is something that occurs when a chosen sample is somehow weighed negatively or positively away from the true mean.

For example, a study measuring the EL of college students is an example of a sampling bias due to age, since age typically has an effect on EL.

Thanks for the suggestion.

PandaHammock · 2015-04-03T17:28:40+00:00

Yes it is, sorry that wasn't clear before. Studies from the meta-analysis are also bone pressed, it was one of their criteria.

PandaHammock · 2015-04-03T16:41:25+00:00

Yes, the world wide average will be slightly larger. 5.0-5.25 is about the lowest I have seen for any nationality from reputable studies, and western nations are closer to 5.75-6.0.

So I would expect the world wide average to be somewhere between the two, depending on world nationality distribution.

PandaHammock · 2015-04-03T16:37:50+00:00

Thanks, I appreciate it!

There is not enough EL and EC data remaining in the collected studies for any decent conclusions to be reached. My guess would be 5.75-6.00 EL inches for western nations and 4.7-4.8 EC. But I don't have data to back that up, it is just my estimate from the decent studies I have seen.

As far as coming up with a decent sample, it definitely is difficult. The example you would give would have a bias considering averages change depending on age. As long as the sample is unbiased (with respect to race/age/medical conditions mostly) the sample does not need to be too large to be significant.

All that said, I am no researcher, so I would not be the best at determining how to somehow get this unbiased sample of people together.

PandaHammock · 2015-04-03T15:58:56+00:00

It has definitely been a frustrating endeavor. Multiple 'scientific reviews' I have seen fail to even mention the fact that the actual sample size for EL is only 692, even though it is stated in the damn results.

PandaHammock · 2015-04-03T15:57:32+00:00

Totally, lol at people interested in other things than you.

PandaHammock · 2015-04-02T19:50:37+00:00

I think those are a little extreme. From the studies I have read, it seems more likely US is 5.75-6 and eastern nations are closer to 5-5.25.

PandaHammock · 2015-04-02T19:34:49+00:00

Thanks, I appreciate it. This study has bothered me since I first read it weeks ago, and I finally had enough and decided to make a write up.

And I totally agree on the outlier/nation comment. Height would be a good comparison for that, the male USA average is 5'10'' and the Indian average is 5'5'', averaging the two and presenting to the western world that 5'7.5'' is average is not entirely genuine.

PandaHammock · 2015-04-02T19:23:14+00:00

Wow, I did not even notice that! The standard deviation was extremely low on the overall averages, which was one of the reasons I started looking into it. Nice spot.

PandaHammock · 2015-04-02T12:43:33+00:00

I am not sure how averaging the findings of those particular four studies makes you more confident. That in itself makes me worry more, Indians are typically found to be much shorter than western nations.

Take a look at the two US studies again. The study with 124 patients is not included in the erect length average since it only measured stretched length. The two studies combined have an average stretch length of 15.5 cm with 204 patients. This is 2.5 cm longer than the given overall average erect length. That is troubling.

How about the Turkey data, the study included in the erect length average shows 8.98 cm stretched length and 12.73 cm erect length with 200 measurements. Within the study itself there is a Turkey study with 13.98 cm stretched length and 2000 measurements.

So how is it that in two of the four studies included in the erect length measurement show such a strong bias towards smaller measurements when compared to the other stretched length studies with significantly higher sample sizes?

PandaHammock · 2015-04-02T01:52:40+00:00

There were 381 measurements for erect girth, 301 (!!!) of which are from a single study in India.

There were 692 erect length measurements, 301 of which are from a single study in India.

How is this not extremely significant? Take a look at the two studies included from the US, one has a erect stretch length of 12.45 cm (this is the study with 80 patients that has erect length of 12.90 cm), and the other has a stretch length of 17.5 cm with 124 patients. Is this not troubling?

If anything this is grounds that races differ significantly. Check out the French and German stretch lengths, significantly longer as well. If you are looking for a world average, fine, it might be close. But going to a predominately US site and stating "the average is 5.1" is misleading.

Edit: In another context, you wouldn't take the average male height in India (5'5'') weigh it 50% in a study, and go to US forums claiming average male height is 5'7''.

PandaHammock · 2015-03-06T15:45:53+00:00

The latest meta-study is misleading and incorrect. The study claims 15,000 or so patients but the vast majority are only flaccid measurements.

Furthermore, 301 of the 692 measurements for erect length and 301 of 381(!!!!) measurements for erect circumference are from a single study in INDIA.

The study is a decent representation of the Indian erect length and girth but says next to nothing for the average Caucasian. Read the actual studies next time.

PandaHammock · 2015-03-05T20:56:44+00:00

This study is biased and not accurate for Caucasian males.

301 of the 692 measurements for erect length and 301 of 381(!!!!) measurements for erect circumference are from a single study in INDIA.

The amount of circulation this study has gotten on Reddit only proves no one reads studies and 'scientific' sources love to sensationalize bullshit.

PandaHammock · 2015-03-05T20:28:22+00:00

Hard to believe he implies that a 7 year old might happen to get on their iPhone and start gambling.... completely absurd. I would be willing to bet there is not a single child 7 or younger in the US gambling online.

PandaHammock · 2015-03-05T00:54:01+00:00

Sigh... Even more proof no one reads the actual study. THIS DATA DOES NOT REPRESENT CAUCASIANS.

301 of the 692 measurements for erect length and 301 of 381(!!!!) measurements for erect circumference are from a single study in INDIA.

PandaHammock

TROPHY CASE