A closely related type of question asks for the expected number out of n items whose values are in a specified range when each independently has a normal distribution.

If each item has probability p of being in this range, we would expect that the number in n items would be:

expected number  =  n×p

Note that this does not need to be a whole number.

To answer the questions below, find the probability that a single item is in the specified range, then use the template at the bottom of the diagram to multiply by the number of items, n.

Repeat with different questions until you have mastered the method.