This column focuses on what statisticians do when they are not being statisticians. If you would like to share your pastime with readers, please email Megan Murphy, Amstat News managing editor.

Moulton after jumping from an airplane in Dubai in October of 2015. Photo by C Laszio

Larry Moulton

Who are you, and what is your statistics position?

My name is Larry Moulton. I am a professor in the department of international health (jointly appointed in the department of biostatistics) in the Johns Hopkins Bloomberg School of Public Health. I mainly design and analyze large, usually randomized, field trials around the world.

Tell us about what you like to do for fun when you are not being a statistician.

I have been a skydiver since I was 19, although there was a near-25-year break in jumping due to the demands of family and career. This is the kind of activity that requires a minimum amount of participation to remain ‘current.’ Currency will keep you from being an undue hazard to yourself or others, as well as help maintain your flying skills so you can frolic with your buddies in freefall.

My typical skydiving day is comprised of 3–5 jumps from 13,500 feet. Each jump starts by choreographing and practicing our planned aerial maneuvers on the ground—it looks a bit like synchronized swimming, as we join in one pattern, let go, and rejoin in another. Then, there is a 15-minute plane ride to the exit altitude, about a minute of freefall, a few minutes gliding about under canopy, and (usually) a soft, stand-up landing.

What drew you to this hobby, and what keeps you interested?

I suppose it was reading a lot of superhero comic books as a child—as an adult, I can dress up in a colorful costume and fly. Although we are all falling relative to each other, skydivers can fly down, up, sideways …

Although, now—especially after my long layoff—I am no longer on the cutting edge. It is still an awful lot of fun! One day of skydiving clears the mind as much as a week of traipsing about a forest. And, as with other sports, there are age-related goals to be attained. Last year, I was part of a 20-way formation that, while not large in itself, was big enough to gain us the Pennsylvania state record for number of skydivers over the age of 60 linked up in freefall (all members of SOS=Skydivers Over Sixty). As I get back into full gear, I am looking forward to national records (for old folks, anyway).

Now for the numbers. When I was a doctoral student, Kung-Yee Liang made the astute observation that my skydiving career could be modeled by a geometric distribution: number of successes until a failure! In the U.S., there is about one fatality for every 165,000 jumps. Among people making a tandem jump (attached to someone who has a twice-as-large parachute), the risk is about 1/500,000. My personal risk is perhaps 1/250,000—worse than a tandem jump, as I am with others in the air and opening the parachute somewhat lower, but not as risky as it is for skydiving students or experienced jumpers who use higher-performance parachutes in ways that give little margin for error. Still, even with the meager 60 or so jumps I make each year (some people will make 1,000 in a year), that is about a 1/4,000 chance skydiving this year will keep me from skydiving next year.