Sunday, September 27, 2009

Wear sunscreen

The press packet for the proposed ban on teenage indoor tanning ban contains one of my all time favorite examples of statistical fear mongering (see page 4):

Using a tanning bed before age 35 increases your risk of developing skin cancer by 75%.

Wow, that is a very scary sounding statistic. However, even if it is true that your odds of developing skin cancer increase by 75% if you use a tanning bed before age 35, the odds that you will be diagnosed with skin cancer are still low.

For example, let’s say that the odds of winning the lottery are 1 in one million. Not very goods odds. Let us suppose that the lottery was changed such that your odds of winning have improved by 75%. Now your odds of winning are about 1 in 571,429. Still not very good odds.

The odds of getting skin cancer are much more likely than the odds of my hypothetical lottery. According the data in the press packet, 18 in 100,000 people across the nation are diagnosed with melanoma each year. Therefore, the odds of any randomly selected individual of being diagnosed with skin cancer this year are 1 in 5,556. It seems very silly to me to ban all teenagers from using tanning beds based on statistical evidence like this. More lives could probably be saved by requiring everyone to wear sunscreen, not that I would be any more supportive of a sunscreen mandate.

Anytime I hear misleading statistics, I am reminded of this joke: A new medicine was being tested on chickens. A sample of sick chickens was given the new medicine. 33% of the chickens in the sample experienced a full recovery, 33% of chickens had no change in their health, but unfortunately the third chicken ran away.