Question 23 • Algebra II
If the company’s claim is correct, the sampling distribution of the mean for 10 students has standard error 3/√10, about 0.95 minutes. The observed mean of 25 minutes is 5 minutes below 30, giving a test statistic of (25 − 30)/0.95 ≈ −5.27, which is far enough from zero to be significant at the 5% level in a two-tailed test. The teacher rejects the claim that the average is 30 minutes; choice B says her students do not, on average, take 30 minutes.
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