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.
[-94.823, 145.396, -61.919, 174.283, 60.137, 50.828, 171.822]