Testing a Claim about a Difference between Means — Quiz
Question 9 • Statistics
A student claims that professional male basketball players are taller, on average, than college male basketball players. To investigate this claim, the student selects a random sample of 30 professional basketball players and 30 college basketball players. The mean height of the sample of professional male basketball players is 76 inches with a standard deviation of 3 point 5 inches. The mean height of the sample of college male basketball players is 74 point 5 inches with a standard deviation of 5 point 5 inches. The student would like to determine if there is convincing evidence that the true mean height of all professional male basketball players is greater than the true mean height of all college male basketball players. The hypotheses ratio of cap h sub 0 to mu sub 1 minus mu sub 2 is equal to 0 , ratio of cap h sub A to mu sub 1 minus mu sub 2 is greater than 0 are tested where mu sub 1 is equal to the true mean height of all professional male basketball players, and mu sub 1 is equal to the true mean height of all college male basketball players. The conditions for inference have been met. What are the values of the test statistic and cap p -value for a t -test about a difference in means? Use the t -table and the z -table.
Answer
A
z is equal to negative 1 point 2 6 . The cap p -value is 0 point 1 0 3 8 .
B
z is equal to 1 point 2 6 . The cap p -value is 0 point 1 0 3 8 .
C
t is equal to negative 1 point 2 6 . The cap p -value is between 0 point 1 0 and 0 point 1 5 .
D
t is equal to 1 point 2 6 . The cap p -value is between 0 point 1 0 and 0 point 1 5 .
Explanation
The estimated difference in sample means is 76 − 74.5 = 1.5 inches. The standard error is √(3.5²/30 + 5.5²/30) ≈ 1.19 inches, so the test statistic is t ≈ 1.5/1.19 = 1.26. For a one-sided test with roughly 49 degrees of freedom, the t-table places the p-value between 0.10 and 0.15, matching choice D: t = 1.26 and a p-value between 0.10 and 0.15.
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