A simple random sample of size n is drawn from a population that is normally distributed. The sample mean,, is found to be 113, and the sample standard
deviation, s, is found to be 15.
NOTE: Find the confidence intervals using your calculator and round your answer to one decimal place and use it to find the margin of error, E.
(a) Construct a 90% confidence interval for u if the sample size, n, is 14.
Answer: The Confidence Interval= ( ), E=
(b) Construct a 90% confidence interval for u if the sample size, n, is 15.
Answer: The Confidence Interval= ( ), E=
How does increasing the sample size affect the margin of error, E?
Answer: Increasing the sample size (increases, decreases) the margin of error.
(c) Construct a 95% confidence interval for µ if the sample size, n, is 14.
Answer: The Confidence Interval= ( ), E=
Compare the results to those obtained in part (a). How does increasing the level of confidence affect the margin of error, E?
Answer: Increasing the level of confidence (increases, decreases) the margin of error.