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.
[115.643, 84.855, 71.644, 101.947, 133.186, 126.685, -23.845, -93.899, 211.429]