Keltham will wait until everyone's raised their hand, and then go to the whiteboard and show how he'd have approximated it:
0. 1/3 * 0.00729^2 + 1/3 * 0.02048^2 + 1/3 * 0.03456 ^ 2 vs. 0.03125^2
1. ~ (2^2 + 3.5^2)/3 vs. 3.1^2
2. ~ (4 + 12.25) / 3 vs. 9.61
3. ~ 5.4 vs. 9.6 (/6 * 10 => proportional to 9 vs. 16)
4. ~ .00054 vs. .00096
"...where step 1 is dropping the first term that's obviously going to end up insignificant, multiplying both sides of everything by 100, and rounding to two significant digits. I mean, we wouldn't do that in Civilization, and here you might not do it in a Science! report, but it's definitely fine in my classes."
"And step 4 is dividing again by 10,000 to put that factor back in, because your experimental report should summarize the absolute likelihood of the data, not just the relative likelihood of the data. Somebody who wants to compare some completely different hypothesis's likelihood, one you didn't even consider, needs the absolute likelihoods to do that - they need the .00054 and .00096 version, not the 9 vs. 16 version."