Question

Delta	US Airways
82.1	60.8
58.8	76.4
60.0	58.9
57.9	68.6
45.2	58.2
68.4	68.3
52.0	71.4
59.6	72.1
67.6	63.1
61.0	73.3
52.7	77.2
71.4	63.0
44.9	81.1
55.9	83.5
86.7	69.0

You are going to test the null hypothesis that the mean fuel efficiency for population 1 (Delta) is less than or equal to (the mean for population 2 - 15); that is H₀: mu₁ <= mu₂ -15 .  What is the test statistic for this test?  Warning: Your answer should be positive, greater than 1 and less than 4.

Suggestion: calculate the summary statistics. Then calculate the statistic in excel and and with a calculator using the summary values so that you can double check your understanding and because on in-class exams you will not have access to excel. Note that in excel this particular hypothesis is not part of excels options so you must either play around with the data or find the statistic using the known formulas.

Answer 1

	Delta	US airways
Mean	61.61333	69.66
Variance	143.4784	61.66686
Observations	15	15

Two sample t-test for equal variances:

df= n1+n2-2 = 28

The test statistic:

Pooled variance:

P-value: 0.03526

The test statisitc is significant and rejects H0. There is sufficient evidence to support the claim.