"Fess up.."

OK. Full Disclosure: I confess. I really do NOT care if it's 2.3 or 2.4!

Saying that, I'm well aware of all the other variations. In fact, I spelled them out. I know how to test for chlorine concentration (I've posted the method a number of times). I know how to calculate pool volume (most use 7.5 gallons for gallons/cubic foot but the more precise number is 7.48). I even realize that drop size changes and the recommended way is to hold the bottle exactly perpendicular.

But I have shown how two separate rounding functions used consecutively have generated an inaccuracy that results in .1 increase above the correct rounded figure.

Is accuracy to 4 decimal places necessary? Sounds petty to say "yes" but it's not. Bleach concentrations go into the formula out to 4 decimal places routinely (5.25% bleach is .0525 in the formula).

We estimate pool volume. We estimate bleach concentration. We even estimate amount of bleach. These are all, to the statistician, known levels of error or "noise" The formula should NOT introduce another level of "noise" if it is not necessary.

Your statement at the top "YES. It's accurate." needs to be amended: Yes, it's accurate to 1 part per million. This is certainly true and I have no problem with that.

However, the calculations CLEARLY show that it is NOT accurate to 0.1 part per million.

Carl