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: [233.848, -58.713, 126.623, 27.615, 62.365, 200.239, 13.38]
Example Output: 86.48

Example Input: [30.7, 241.916, 245.677, -26.708, 212.446, 81.786, 208.412, 237.096, 155.359]
Example Output: 154.076

Example Input: [-77.098, 33.981, 159.723, -56.151, 9.713, -89.709, 12.851]
Example Output:
-0.956