Probabilities of failing birth control methods

Sep 15, 2014

In high school health class, where I learned about contraceptives and the dangers of pre-marital sex, my teacher spouted rates to scare. He would say something like condoms are 98 percent effective but never explained what that meant. Do they break 2 percent of the time? Do couples get pregnant 2 percent of the time? STDs?

These charts from Gregor Aisch and Bill Marsh might help. They show the probability of an unplanned pregnancy, categorized by contraceptive and over a span of ten years. The top solid lines represent probabilities with “typical use” and the dashed lines on the bottom represent probabilities with “perfect use.”

Maybe it’s time for better instructions on how to use these things.

Update: The calculation of long-term probabilities is likely on the pessimistic side and makes too many assumptions about the data and population. Andrew Whitby critiques.


Years You Have Left to Live, Probably

The individual data points of life are much less predictable than the average. Here’s a simulation that shows you how much time is left on the clock.

10 Best Data Visualization Projects of 2015

These are my picks for the best of 2015. As usual, they could easily appear in a different order on a different day, and there are projects not on the list that were also excellent.

The Best Data Visualization Projects of 2011

I almost didn’t make a best-of list this year, but …

Think Like a Statistician – Without the Math

I call myself a statistician, because, well, I’m a statistics graduate student. However, the most important things I’ve learned are less formal, but have proven extremely useful when working/playing with data.