`mean``items`procedurereturns the arithmetic mean of the

`items`(the sum of the numbers divided by the number of numbers).(mean '(1 2 3 4 5)) => 3

`mean``items`procedurereturns the arithmetic mean of the

`items`(the sum of the numbers divided by the number of numbers).(mean '(1 2 3 4 5)) => 3