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Statistical inference — Question 9

QCAA 2020, Paper 1 · 1 mark

Q9 · 2020 · Technology-freeSimple familiar1 mark

QUESTION 9

The scores on a test are assumed to be normally distributed.
Researchers use the results from a random sample of scores to calculate a confidence interval for the population mean. However, a shorter confidence interval width is required so the researchers decide to use a second sample for their calculations.
Assuming that the standard deviations for both samples are the same, the researchers can ensure that a shorter confidence interval width is produced by
(A)
decreasing the sample size and decreasing the confidence level.
(B)
decreasing the sample size and increasing the confidence level.
(C)
increasing the sample size and decreasing the confidence level.
(D)
increasing the sample size and increasing the confidence level.
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