Suppose that the times to complete an obstacle course are normally distributed with an unknown mean and standard deviation. A random sample of18

course times is taken and gives a sample mean of105

seconds and a sample standard deviation of18

seconds.

(a)The EBM, margin of error, for a98%

confidence interval estimate for the population mean using the Student'st

-distribution is10.89

.

(b) Find a98%

confidence interval estimate for the population mean using the Student'st

-distribution.

• Round the final answers to two decimal places.