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A random sample of 200 students in a statistics class revealed a mean test score of...

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.

Math   Statistics-And-Probability   
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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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