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: [159.291, 160.61, -50.992, 34.053, 78.883, 222.627, 105.95]
Example Output: 101.489

Example Input: [-81.432, -63.059, 150.144, 55.203, 215.405, -89.797, 72.946]
Example Output: 37.059

Example Input: [138.493, 120.089, -77.302, -6.35, 147.393, 174.535, 54.408, -43.141]
Example Output:
63.516