Question

Please type answer, can't see written answers well.

Also PLEASE PROVIDE BELL SHAPED CURVE** That is the part I struggle with the most.

Baggage fees charged by airlines have received much attention recently as the industry has looked for ways to increase revenue without directly increasing fares. American Airlines would like to investigate if the average number of bags checked per flight fell after the company implemented fees for checking them. The following table shows the average numbers of checked bags per flight for a random sample of Boeing 737 domestic flights both before and after the fees were implemented.

Before After

n1 = 44 n2 = 55

x1 = 108.2 x2 = 104.7

σ1 = 9.6 σ2 = 9.3

a. Construct a 90% confidence interval to estimate the difference in the average number of bags per flight before and after the fees were implemented.

b. Perform a hypothesis test using α = .05 to determine if the  average number of checked bags decreased after the checked baggage fees were administered.

c. Determine the p-value and interpret the results.

Answer 1

a) At 90% confidence interval, the critical value is z_0.05 = 1.645

The 90% confidence interval is

+/- z_0.05 *

= (108.2 - 104.7) +/- 1.645 * sqrt((9.6)^2/44 + (9.3)^2/55)

= 3.5 +/- 3.15

= 0.35, 6.65

b) H₀:

H₁:

The test statistic z = ()/

= (108.2 - 104.7)/sqrt((9.6)^2/44 + (9.3)^2/55)

= 1.83

At alpha = 0.05, the critical value is z_0.05 = 1.645

Since the test statistic value is greater than the critical value (1.83 > 1.645), so we should reject the null hypothesis.

At 0.05 significance level, there is sufficient evidence to conclude that the average number of checked bags decreased after the checked baggage fees were administered.

C) P-value = P(Z > 1.83)

= 1 - P(Z < 1.83)

= 1 - 0.9664 = 0.0336