The standard deviation of test scores on a certain achievement test is 10.5. A random sample...

The standard deviation of test scores on a certain achievement test is 10.5. A random sample of 150 scores on this test had a mean of 76.2. Based on this sample, find a 90% confidence interval for the true mean of all scores. Then complete the table below.

Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place.

What is the lower limit of the 90 confidence interval?
What is the upper limit of the 90% confidence interval?

Expert Solution

We have given that,

Sample mean =76.2
Population standard deviation=10.5
Sample size=150
Level of significance =   1-0.90=0.1
Z critical value (by using Z table)=1.645

Confidence interval formula is

=(74.8,77.6)

lower limit of the 90 confidence interval=74.8
upper limit of the 90% confidence interval=77.6

orchestra answered 1 year ago

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