8) Respond to the question of the confidence interval. Round to four decimal pla
ID: 3338634 • Letter: 8
Question
8) Respond to the question of the confidence interval. Round to four decimal places. Write only a number as your answer.
A)
A simple random sample of 12 e-readers of a certain type had the following minutes of battery life.
287, 311, 262, 392, 313, 316, 335, 316, 286, 264, 264, 291
Assume that it is reasonable to believe that the population is approximately normal and the population standard deviation is 79. What is the upper bound of the 95% confidence interval for the battery life for all e-readers of this type?
B)
Following are interest rates (annual percentage rates) for a 30-year-fixed-rate mortgage from a sample of lenders in a certain city. It is reasonable to assume that the population is approximately normal.
4.327, 4.461, 4.547, 4.717, 4.365, 4.708, 4.842
Find the upper bound of the 99% confidence interval for the mean rate.
Explanation / Answer
A) The statistical software output for this problem is:
One sample Z confidence interval:
: Mean of variable
Standard deviation = 79
95% confidence interval results:
Hence,
Upper bound of 95% confidence interval = 347.7810
B) The statistical software output for this problem is:
One sample T confidence interval:
: Mean of variable
99% confidence interval results:
Hence,
Upper bound of 99% confidence interval = 4.8399
Variable n Sample Mean Std. Err. L. Limit U. Limit Data 12 303.08333 22.805336 258.3857 347.78097Related Questions
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