Question

A random sample of 200 students in a statistics class revealed a mean test score of 78. If the standard deviation of the population was 5.5, ﬁnd the 90% conﬁdence interval for the unknown population mean test score.

Answer #1

We have given that,

Sample mean =78

Population standard deviation=5.5

Sample size=200

Z critical value (by using Z table)=1.645

Confidence interval formula is

=(77.36,78.64)

Lower confidence limit =77.36

Upper confidence limit =78.64

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