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.
[-7.151, -9.873, 208.875, 227.477, 102.689, -9.211, -87.729, 58.21, 38.21, 183.337]