22
QuizMultiple Choice

N/A — Exam

Question 22 • Statistics

The proportion of all US adults who eat popcorn when they go to the movie theater is p is equal to 0 point 8 7 A random sample of 20 US adults was selected and asked if they eat popcorn when they go to the movie theater. Which of the following is the shape of the sampling distribution of hat p ?

Answer
A
Because n times 1 minus p minus 20 times 1 minus 0 point 8 7 minus 2 point 6 is less than 10 , the sampling distribution of hat p is not approximately Normal. Because p is equal to 0 point 8 7 is closer to 1 than 0 , the sampling distribution of hat p is skewed to the right.
B
The sampling distribution of hat p is approximately Normal because .
C
Because n times 1 minus p minus 20 times 1 minus 0 point 8 7 minus 2 point 6 is less than 10 , the sampling distribution of hat p is not approximately Normal. Because p is equal to 0 point 8 7 is closer to 1 than 0 , the sampling distribution of hat p is skewed to the left.
D
Because n times 1 minus p minus 20 times 1 minus 0 point 8 7 minus 2 point 6 is less than 10 , the sampling distribution of hat p is not approximately Normal. The sampling distribution of hat p is skewed right and centered at 0 point 8 7 .

Explanation

For the sampling distribution of the sample proportion, the success-failure condition requires both np and n(1 − p) to be at least 10. Here, n(1 − p) = 20(1 − 0.87) = 2.6, so the distribution is not approximately Normal. Since p = 0.87 is close to 1, sample proportions tend to be near the high end, with a tail toward lower values; the distribution is skewed to the left. Choice C describes this shape.

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