Question

Consumer Reports rated airlines and found that 80% of the flights involved in the study arrived on time (that is, within 15 minutes of scheduled arrival time). Assuming that the on-time arrival rate is representative of the entire commercial airline industry, consider a random sample of 180 flights. (Round your answers to two decimal places.)
What is the expected number that will arrive on time?
What is the standard deviation of this distribution?

Answer 1

Answer:

Expected number = mean = 144

Standard deviation = 5.37

Step-by-step explanation:

As you have two options (on time / delay) we are talking about using a Binomial distribution.

Expected number that will arrive on time  is the same as expected value (mean).

mean = expected value = np = (180)(0.8) = 144

std dev = √[np{1-p)] = √[180{0.8*(1-0.8)}] =√[180{0.8*0.2)}] = 5.37