Calculate the margin of error for a derived ratio

moe_ratio(num, denom, moe_num, moe_denom)

## Arguments

num

The numerator involved in the ratio calculation (an estimate)

denom

The denominator involved in the ratio calculation (an estimate)

moe_num

The margin of error of the numerator

moe_denom

The margin of error of the denominator

## Value

A margin of error for a derived ratio