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.
[133.83, 197.316, 12.833, 184.319, -40.383, 246.592, 21.652, -3.563]