The standard error of a ratio of two sample estimates, x and y, is approximately equal to (begin
parenthesis) x divided by y (end parenthesis) times the square root of (begin parenthesis) (begin
parenthesis) the standard error of x divided by x (end parenthesis) squared plus (begin
parenthesis) the standard error y divided by y (end parenthesis) squared minus (begin
parenthesis) two times the correlation coefficient r times (begin parenthesis) the standard error of
x divided by x (end parenthesis) times (begin parenthesis) the standard error of y divided by y
(end parenthesis) (end parenthesis) (end parenthesis).