I didn’t notice this at first but upon reviewing the CFAI mocks/tests, something odd struck me: there doesn’t seem to be consistency in terms of when I should use the approximate x-standard deviations from mean figure and when I should use the exact one.

Example 1 (from one of the mocks):

Needed to calculate what results fall within the 95% confidence interval. According to the answer, I’m supposed to use 1.96 instead of the rounded 2.

Cotrast this with:

Example 2: Quanitative methods assessment:

What results fall within the 99% confidence interval? Well the exact number is 2.58 but the answer uses a very rounded 3 for this.

How am I supposed to know which one to go for? I guess I could just try both ones and whichever has the answer as one of the options is the one I’m meant to pick, but that doesn’t sound right to me.

Am I missing something?