Using Excel formulas
=LARGE(A1:A20, 1)/COUNT (A1:A20)
Count (Ai:An) Function that allows to count the total number of values in a cells range between Ai and An that contain only numbers.
Large (Ai:An, k) Function that allows to find the value of the largest number in a cells range between Ai and An, the number k determine the k-th largest value