QUESTION 1
Find the confidence interval specified. Assume that the population is normally distributed.
Thirty randomly selected students took the calculus final. If the sample mean was 81 and the standard deviation was 9.3, construct a
78.12 to 83.88
76.34 to 85.66
76.82 to 85.18
76.32 to 85.68
6.67 points
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The correct confidence interval is
Step 1 :To construct a 99% confidence interval for the mean score of all students, the formula is
Step 2 :The sample mean
Step 3 :For a 99% confidence level, the z-score
Step 4 :The margin of error
Step 5 :Substituting the known values gives
Step 6 :The confidence interval is then
Step 7 :Calculating the lower and upper bounds gives
Step 8 :The confidence interval is
Step 9 :Rounding to two decimal places, the confidence interval is
Step 10 :Comparing with the given options, the closest is
Step 11 :The correct confidence interval is