Question

A leading magazine (like Barron's) reported at one time that the average number of weeks an individual is unemployed is 40 weeks. Assume that for the population of all unemployed individuals the population mean length of unemployment is 40 weeks and that the population standard deviation is 3.2 weeks. Suppose you would like to select a random sample of 79 unemployed individuals for a follow-up study.

Find the probability that a single randomly selected value is greater than 40.6. P(X > 40.6) = (Enter your answers as numbers accurate to 4 decimal places.)

Find the probability that a sample of size n = 79 n = 79 is randomly selected with a mean greater than 40.6. P(M > 40.6) =

(Enter your answers as numbers accurate to 4 decimal places.)

Answer 1

Solution :

Given that ,

mean = = 40

standard deviation = = 3.2

1)

P(x > 40.6) = 1 - P(x < 40.6)

= 1 - P((x - ) / < (40.6 - 40) / 3.2)

= 1 - P(z < 0.19)

= 1 - 0.5753 Using standard normal table.

= 0.4247

Probability = 0.4247

2)

n = 79

=   = 40 and

= / n = 3.2 / 79 = 0.3600

P(M > 40.6) = 1 - P(M < 4.06)

= 1 - P((M - ) / < (40.6 - 40) / 0.3600 )

= 1 - P(z < 1.67)

= 1 - 0.9525 Using standard normal table.

= 0.0475

Probability = 0.0475