Question

"The rates of on-time flights for commercial jets are continuously tracked by the U.S. Department of Transportation. Recently, Southwest Air had the best rate with 80 % of its flights arriving on time. A test is conducted by randomly selecting 15 Southwest flights and observing whether they arrive on time. (a) Find the probability that at least 3 flights arrive on time."

Answer 1

You have to use the binomial distribution formula:

`(n!)/(k!(n-k)!)p^(k)(1-p)^((n-k))`

where

n is the sample size: 15 flights

k is the nuber of successes: 3 flights

p is the probability of success: 0.80

`(15!)/(3!12!)p^(3)(0.20)^((12))=9.5420416E-7`