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: [15.293, 221.056, 241.387, 81.3, 102.644, 146.885, -33.65, -36.56, -69.176]
Example Output: 74.353

Example Input: [219.428, 229.08, 24.616, -83.165, -28.839, 195.219, 170.491, -78.673]
Example Output: 81.02

Example Input: [-15.842, 203.934, 1.146, 230.272, 145.962, 67.736, 119.41, 205.691, 148.317]
Example Output:
122.958