Recall that the expected value is another way to refer to µ. What is really being asked is how many calls are expected to come in during a 5-minute interval. The following conversion factor can be used to find the mean number of calls per minute when given the mean number of calls per hour. calls hour · 1 hour 60 minutes Convert 24 calls per hour to calls per minute. 24 calls hour · 1 hour 60 minutes = calls per minute To find the expected number of calls per a 5-minute interval, multiply the mean number of calls per minute by 5. (5 minutes)(mean number of calls per minute) = 5 = calls per 5 minutes