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.
[148.686, 15.171, 231.446, -26.126, 176.16, -52.493, 27.957]