In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.

Example Input: [214.656, -82.183, 105.038, -34.9, -44.836, 143.236, 183.045, 160.483, 34.398]
Example Output: 75.437

Example Input: [171.805, 71.031, 36.192, 28.948, -58.045, 53.843]
Example Output: 50.629

Example Input: [156.951, 30.808, 141.058, 178.168, 65.522, -4.456, -28.233, 139.967]
Example Output:
84.973