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: [150.321, 169.658, 221.448, 54.785, 160.245, 9.534, 78.865, 229.753, 225.969]
Example Output: 144.509

Example Input: [194.983, -22.961, 95.798, -2.34, 178.547, -90.942, 122.52, 109.389]
Example Output: 73.124

Example Input: [-84.874, 212.839, 150.182]
Example Output:
92.716