Answer:
Step-by-step explanation:
We want to determine a 98% confidence interval for the mean price for textbooks.
Number of sample, n = 42
Mean, u = $114.5
Standard deviation, s = $12.3
For a confidence level of 98%, the corresponding z value is 2.33.
We will apply the formula
Confidence interval
= mean ± z ×standard deviation/√n
It becomes
114.5 ± 2.33 × 12.3/√42
= 114.5 ± 2.33 × 1.898
= 114.5 ± 4.42
The lower end of the confidence interval is 114.5 - 4.42 = 110.08
The upper end of the confidence interval is 114.5 + 4.42 = 118.92
Therefore, with 98% confidence interval, the mean price of all textbooks is between $110.08 and $118.92
