Concept explainers
a)
To findthe critical value z for 98% confidence interval for a proportion.
a)
Answer to Problem 35E
The critical value z for 98% confidence interval for a proportion is 2.33
Explanation of Solution
Given:
Confidence level = 0.98
The confidence level = 0.98.
So, level of significance = 0.02
The zc critical value = 2.33 …Using excel formula, =ABS(NORMSINV(0.02/2))
b)
To construct 98% confidence interval for a proportion.
b)
Answer to Problem 35E
The 98% confidence interval for a proportion is 0.1859 < p < 0.2133
Explanation of Solution
Given:
Confidence level = 0.98
The zc critical value = 2.33
Formula:
Sample proportion:
Margin of error:
The confidence interval:
The sample proportion is,
The margin of error is,
The confidence interval is,
Hence, the 98% confidence interval for population proportion is 0.1859 < p < 0.2133
c)
To interpret confidence interval.
c)
Answer to Problem 35E
We are 98% confident that the true population proportion is between 0.1859 and 0.2133
Explanation of Solution
Given:
The 98% confidence interval for population proportion is 0.1859 < p < 0.2133
We are 98% confident that the true population proportion of all American adults who would report having earned money by selling something online in the previous year is between 0.1859 and 0.2133
Chapter 8 Solutions
PRACTICE OF STATISTICS F/AP EXAM
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