If you are asked to estimate a number that is a product (or sum) of many numbers, and you have good estimates for all those numbers but one, well variance in that last number you can’t estimate well will dominate the variance of your answer. It just takes one.
If you are asked to estimate a number that is a product (or sum) of many numbers, and you have good estimates for all those numbers but one, well variance in that last number you can’t estimate well will dominate the variance of your answer. It just takes one.