The idea is simple and deep: people submit a head to toe photo of themselves along with their height and weight. Then Rob puts it in the corresponding empty square on his chart. So far, 193 photos have been placed on the chart, both men and women together.
Here's how it work:
Height increases from bottom to top, from 4 ft 10 in. to 6 ft 8 in., each row counting for one more inch.
Weight increases from left to right, from 90 lbs to 380 lbs, each column standing for 10-lbs increment.
The diagonal pattern forming in the center of the chart is also to be found in a BMI chart. The Body Mass Index is defined as the individual's body weight divided by the square of his or her height.
Overlaying BMI lines over Rob's chart gives you this picture below. The leftmost line is BMI = 18 and the next one right to it is BMI = 25. Anyone in between these two lines has a healthy weight, according to insurers science. The next lines from left to right are BMI = 30, 35, 40, 45, 50, and 55.
It should come as no surprise that more people will found themselves in the 18-25 range than on any other area of the chart. Rob's sample obeys the same rules of ramdomness found in any poll or public survey. Unless there is something very special no one knows about about sending a photo of oneself over the web, all kinds of people should be willing to participate without skewing the stats intentionally.This bar chart shows how many submissions Rob got for each 5-BMI unit range. This is close to the normal weight distribution in the US population. One has to remember that Rob counts only one submission for each square in his chart. While he must be receiving several submissions for the most frequent height/weight combinations, he's keeping only one for display.
When all squares will be filled in, the chart will somehow flatten and this will be skewed stats. Counting all real submissions should rather tend toward showing the normal distribution.One final note:
To get a BMI of 55, one has to be something like 4' 10" and 380 lbs. No one of that size has participated in Rob's experiment yet but it's live since last year only.
There is plenty of empty squares left in the chart just waiting for volunteers. I guess Rob is still taking entries this year too so if you feel like it, just take a photo of yourself and send him an e-mail.
Here's the instructions about how to do it.