AP Statistics · Topic 7.3
Justifying a Claim About a Population Mean Based on a Confidence Interval Practice
Part of Inference for Quantitative Data: Means.(UNC-4.F)
Practice questions
5
Sample questions
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Sample 1difficulty 1/5
A 90% confidence interval for the mean weight of adult salmon is (4.2, 4.8) kg.
Which is a correct interpretation?
- Acheck_circle
We are 90% confident the population mean weight is between 4.2 and 4.8 kg.
- B
90% of samples will have a mean between 4.2 and 4.8 kg.
- C
There is a 90% probability that the true mean is in this interval.
- D
90% of adult salmon weigh between 4.2 and 4.8 kg.
Why
A confidence interval describes our confidence in capturing the population parameter, not individual values, probability, or future samples.
- A
Sample 2difficulty 1/5
A statistician constructs many 95% confidence intervals for a population mean using independent random samples.
Which statement best describes the meaning of "95% confidence"?
- A
The probability that any one interval contains the mean is 0.95.
- B
The sample mean lies in 95% of intervals.
- Ccheck_circle
About 95% of such intervals would capture the true population mean.
- D
95% of the data will fall within the interval.
Why
Confidence level refers to the long-run capture rate of the procedure across repeated samples.
- A
Sample 3difficulty 3/5
"We are 90% confident that μ is between 50 and 56" interprets a
- A
Mean
- Bcheck_circle
90% CI
- C
Type I error
- D
Significance level
Why
Standard CI interpretation.
- A
Sample 4difficulty 3/5
A 95% CI for mean reaction time of (240, 280) ms means
- A
Mean is exactly 260 ms
- B
95% of subjects respond between 240–280 ms
- C
Reaction times average 95% accurate
- Dcheck_circle
We are 95% confident mean reaction time is between 240 and 280 ms
Why
CI describes the parameter, not individual values.
- A
Sample 5difficulty 3/5
A 95% CI for μ is computed as (10.5, 13.5). The point estimate is
- A
1.5
- B
10.5
- Ccheck_circle
12.0
- D
13.5
Why
Midpoint = (10.5 + 13.5)/2 = 12.0.
- A