Question

A simple random sample is drawn from a normally distributed population, and when making a statistical inference about the population mean, the margin of error is found to be 5.9 at a 95% level of confidence. if the mean of the sample is 18.7, what is the 95% confidence interval for the population mean? 18.7 ± 5.9 18.7 ± 9.7 18.7 ± 11.6 18.7 ± 15.2

Answer 1

If the mean of the sample is 18.7, The 95% confidence interval for the population mean is 18.7 ± 11.6.

Confidence interval

z-score for 95% confidence interval =1.96

Lower limit of the interval:

Lower limit=Sample mean-(Z-score×Margin of error)

Lower limit=18.7-(1.96×5.9)

Lower limit=18.7-11.564

Lower limit=18.7-11.6 (Approximately)

Upper limit of the interval:

Upper limit=Sample mean+(Z-score×Margin of error)

Upper  limit=18.7+(1.96×5.9)

Upper  limit=18.7+11.564

Upperr limit=18.7+11.6 (Approximately)

Hence:

Confidence interval= 18.7 ± 11.6

Therefore the 95% confidence interval for the population mean is 18.7 ± 11.6.

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