Question

Suppose the round-trip airfare between Philadelphia and Los Angeles a month before the departure date follows the normal probability distribution with a mean of $387.20 and a standard deviation of $68.50. What is the probability that a randomly selected airfare between these two cities will be more than $450?

A.

0.3669

B.

0.0788

C.

0.1788

D.

0.2033

Answer 1

The round-trip airfare between Philadelphia and Los Angeles a month before the departure date follows the normal probability distribution with mean μ = $387.20 and standard deviation σ = $68.50.

Use the standardisation for solving this problem,

P (X > 450) = P {(X – μ) / σ > (450 – 387.20) / 68.50}

                               = P (Z > 0.917)

                              = 1 - P (Z ≤ 0.92)

                              = 1 – 0.8212….. (From the standard normal table)

                              = 0.1788

The probability that a randomly selected airfare between these two cities will be more than $450 is 0.1788