The RunKeeper Mystery


Today I went for a run with my friend Jess. We ran side by side and both used RunKeeper on our iPhones (both with Verizon service). At the end of our run, I ended up with 5.03 miles and she ended up with 5.22 miles.

A friend asked if I’d used anything else to map it out, so I tried MapMyRun, which gave me 5.06 miles (using the out-and-back route setting).

Screen Shot 2014-04-27 at 2.49.37 PM

The Math Problem:
Using the stats of your choice (explain why you chose them):
1) What is the absolute error?
2) What is the percent error?
3) Explain how we could get such different results.



  • Kristina

    Thanks! A non-runner friend pointed out that it’s only 4% error, but to runner friends, that extra 0.19 miles matters a lot. Very interested to find out what the acceptable margin for error is for iPhone GPS!

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