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Question 699
Statistics → Epidemiology
Classification
Question
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Confidence interval and sample size
Question Stem
A study is repeated in a similar population using a substantially larger sample. What change in the confidence interval would usually be expected?
Options
A
It becomes wider
B
It becomes narrower
C
It necessarily crosses zero
D
The confidence level automatically changes from 95% to 99%
E
It becomes independent of sampling variability
Explanation
Increasing the sample size improves the precision of an estimate and therefore generally reduces the width of its confidence interval. Increasing sample size does not automatically alter the selected confidence level.
Option Validity
A) increasing sample size generally narrows rather than widens the interval.
C) increasing sample size does not require the interval to cross zero.
D) the selected confidence level does not automatically change with sample size.
E) sampling variability remains relevant, although precision improves.
Further Reading
Review the relationship between sample size, precision and confidence-interval width.