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5 questions · Shuffled order · Untimed practice
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In a simple random sample of 300 people from a population of 12,500, 96 use a service. All selected people respond. Estimate the number in the full population who use the service.
Enter an integer, decimal or fraction without units. Use up to 5 characters, or 6 including a leading minus.
Answer: 4,000
The estimated share is 96/300
Review worked example 6.02.
A population mean is estimated as 18.6 with a margin of error of 0.8. What is the upper endpoint of the reported interval?
Enter an integer, decimal or fraction without units. Use up to 5 characters, or 6 including a leading minus.
Answer: 19.4
Add the margin once: 18.6 + 0.8
Review worked example 6.04.
A population percentage is estimated as 47% ± 3 percentage points. Which statement is justified?
Answer: B
Subtract and add 3 percentage points to 47% to obtain [44%, 50%]. This interval does not establish a share strictly above 50%, and an interval endpoint is not an absolute logical limit on the unknown parameter.
Review worked example 6.09.
For a supplied model E = k/, a sample of 400 gives margin of error 6. Keeping k fixed, what sample size gives margin of error 2?
Enter an integer, decimal or fraction without units. Use up to 5 characters, or 6 including a leading minus.
Answer: 3,600
The margin must be divided by 3, so the square root of sample size must be multiplied by 3. Sample size must therefore be multiplied by 32
Review worked example 6.11.
A reported 95% confidence interval for a population mean is [20, 24]. Which statement is correct?
Answer: C
The target is a population mean, not a collection of individual values. Under valid repeated sampling and the method’s assumptions, about 95% of intervals constructed this way would cover the fixed population mean. This particular interval either covers it or does not; coverage is not guaranteed.
Review worked example 6.05.
Review Sample-based inference and margin of error