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.
[237.061, 157.598, 239.678, 135.432, 186.198, -70.821, 237.869, -66.916]