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The average return on the Dow Jones Industrial Average for 121 quarterly observations is 1.5%. If the standard deviation of the returns can be assumed to be 8%, what is the 99% confidence interval for the quarterly returns of the Dow Jones?
A
[-0.4%; 3.4%]
B
[0.1%; 2.9%]
C
[-6.5%; 9.5%]
D
[-0.1%; 2.9%]
Explanation:
To calculate the 99% confidence interval for the quarterly returns, we use the formula:
Standard error of the sample mean =
Given:
Step 1: Calculate standard error
Step 2: Find critical z-value For 99% confidence interval, the critical z-value is 2.575
Step 3: Calculate margin of error
Step 4: Calculate confidence interval
Therefore, the 99% confidence interval is approximately [-0.37%; 3.37%], which matches option A [-0.4%; 3.4%].