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An existing inventory for a test measuring self-esteem indicates that the scores have a standard deviation of 12. A psycholog
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Answer #1

Sol:

90% confidence interval for mean test scores

xbar-z*sigma/sqrt(n),xbar+z*sigma/sqrt(n)

z crit for 90%=1.645

xbar=65

sigma=12

n=100

65-1.645*12/sqrt(100),65+1.645*12/sqrt(100)

63.026,66.974

ANSWER:

90% lower limit mean=63.0

90% upper limit mean=67.0

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