Hi @emilioalzamora1 I can't recall seeing such a formula but, in theory, it seems deducable as you suggest: the numerator is a sample mean statistic and the denominator is a sample variance such that their ratio would have a standard error. It's just a matter of deriving (finding) the formula for the standard error (for the ratio, of course); then it's a very common step to infer required sample size given a desired margin of error/confidence level. It's a great thought, I'm surprised I haven't run across it ... I copied it to my evernote in case I get some time to go look. Thanks!
Excellent piece! Need some time to digest first of all.
By the way, great profile picture. From where are the GARP pens? Usually one only gets to for one exam