Question

The personnel office at a large electronics firm regularly schedules job interviews and maintains records of the interviews. From the past records, they have found that the length of a first interview is normally distributed, with mean μ = 36 minutes and standard deviation σ = 7 minutes. (Round your answers to four decimal places.)

(a) What is the probability that a first interview will last 40 minutes or longer?

(b) Thirteen interviews are usually scheduled per day. What is the probability that the average length of time for the thirteen interviews will be 40 minutes or longer?

Answer 1

(A) we have to find probability of 40 or longer

using normalcdf

setting lower = 40, upper = 9999, mean = 36 and standard deviation = 7

=normalcdf(lower, upper, mean, standard deviation)

= normalcdf(40,9999,36,7)

= 0.2839

(B) we have to find the probability of a sample mean of 40 or longer

using normalcdf

setting lower = 40, upper = 9999, mean = 36 and standard deviation = 7/sqrt(13) = 1.94

=normalcdf(lower, upper, mean, standard deviation)

= normalcdf(40,9999,36,1.94)

= 0.0197