In the United Kingdom, the more mobile phone towers a county has, the more babies are born there every year. In fact, for every extra cell phone tower beyond the average number, a county will see 17.6 more babies. Is this evidence that cell phone signals have some nefarious baby-making effect on the human body?
Nope. Instead, it's a simple example of why correlation and causation should never be mistaken for the same thing. Writes Matt Parker in the Gaurdian:
This was discovered by taking the publicly available data on the number of mobile phone masts in each county across the United Kingdom and then matching it against the live birth data for the same counties. When a regression line is calculated it has a "correlation coefficient" (a measure of how good the match is) of 98.1 out of 100. To be "statistically significant" a pattern in a dataset needs to be less than 5% likely to be found in random data (known as a "p-value"), and the masts-births correlation only has a 0.00003% probability of occurring by chance.
The match between mobile phone towers and birth rates is an extremely strong correlation and it is highly statistically significant. … Mobile phone masts, however, have absolutely no bearing on the number of births. There is no causal link between the masts and the births despite the strong correlation. Both the number of mobile phone transmitters and the number of live births are linked to a third, independent factor: the local population size. As the population of an area goes up, so do both the number of mobile phone users and the number people giving birth.
But wait, there's more! To test the media's science savvy, Parker sent out a press release detailing the correlation he found—but without any information on the real cause of both factors. Interesting object lesson or in-real-life trolling? Can't it be both? The press release went out late last week. If you've spotted any stories about the fertility powers of cell phone towers, leave a link in the comments.
(Via Steve Silberman)