Some time ago, our charts developer, Mike Danziger, noticed a strange issue that was showing up for some user-entered lab results. See if you can spot it:
Surely this user didn't actually enter a result of 119.66000000000001 mg/dL for their cholesterol reading. No blood test is that precise, right?
No, of course they didn't. What we're seeing here is a result of floating-point error. Floating-point error happens because in most cases, computers represent fractional numbers in base 2, in which it's often impossible to represent a base-10 fraction in a finite number of digits, so rounding happens. These tiny errors can become larger the more calculations you perform, due to compounding effects.