APFIVE Properties of a Two-Sample T-Interval
All of the following statements regarding the construction of a confidence interval for the difference of two means are true except:
| Department | Mean Accidents | Std. Dev. | Sample Size |
|---|---|---|---|
| First Department | 12.3 | 3.5 | 30 |
| Second Department | 7.6 | 3.4 | 30 |
A
Increasing the sample sizes, while keeping other factors constant, will narrow the confidence interval for the difference of means.
B
The confidence interval is computed as the difference of sample means plus or minus the product of the t-critical value and the standard error of the difference.
C
When constructing a confidence interval for the difference between two means, the data must come from paired samples.
D
A t-interval is appropriate for estimating the difference between two means when the population standard deviations are unknown.
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