APFIVE Confidence Interval Critical Value Error
A researcher surveying 550 young adults finds a sample proportion of $$\hat{p} = 0.42$$ and attempts to create a 99% confidence interval. However, she mistakenly uses a z-value of $$2.33$$ instead of the appropriate critical value of $$2.576$$. What experimental mistake did she commit?
TABLE: Confidence Interval Calculation
| Sample Proportion | z-value used | Correct z-value |
| 0.42 | 2.33 | 2.576 |
A
She misinterpreted the confidence level as exceeding 99%.
B
She should have used the $$t$$-distribution since the population standard deviation is unknown.
C
She incorrectly calculated the standard error instead of the critical value.
D
She confused the sample size with the margin of error.
E
She used the incorrect critical z-value for a 99% confidence level.
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