A sample of 20 heads of lettuce was selected. Assume that the population distribution of head weight is normal. The weight of each head of lettuce was then recorded. The mean weight was 2.2 pounds with a standard deviation of 0.1 pounds. The population standard deviation is known to be 0.2 pounds.

Which distribution should you use for this problem? (Round your answers to two decimal places.)

X~

?

U

N

H

Exp

B

,