Sample mean vs. Theoretical mean

The app will take a sample from a discrete uniform distribution, which includes the numbers one through nine, and calculate the sample's mean. You can adjust the size of the sample using the slider. Note that the expected value of this distribution is five.

A sample is taken, and you win twenty dollars if the sample's mean is less than four. There's a catch: you get to pick the sample's size.

Which sample size is most likely to win you the twenty dollars?