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You are in charge of purchasing airplanes for a major airline. You are looking a

ID: 3323950 • Letter: Y

Question

You are in charge of purchasing airplanes for a major airline. You are looking at two planes: the Aircab Type 30, and the Boing-Boing Dasher. The Type 30 is somewhat cheaper than the Dasher, but the airline's operations manager is concerned about fuel consumption. She tells you, "We've seen extensive tests of both planes. Most recently we had tests of 30 Dashers and 35 Type 30's. The Dasher uses an average of 950 gallons of fuel per flight hour with a standard deviation of 42 gallons. The Type 30 only uses 930 gallons per flight hour, but the empirical data shows a standard deviation of 45 gallons. Can you tell me if there's indeed a significant difference between the fuel consumption of the two planes?"

You know that you'll start with a test statistic. What do you calculate?

A) z = 0.72

Explanation / Answer

The statistical software output for this problem is:

Two sample Z summary hypothesis test:
1 : Mean of population 1 (Std. dev. = 42)
2 : Mean of population 2 (Std. dev. = 45)
1 - 2 : Difference between two means
H0 : 1 - 2 = 0
HA : 1 - 2 0

Hypothesis test results:

Hence,

z = 1.85

Option B is correct.

Difference n1 n2 Sample mean Std. err. Z-stat P-value 1 - 2 30 35 20 10.800794 1.8517158 0.0641
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