The mean time taken to design a house plan by40

architects was found to be20

hours with a standard deviation of3.05

hours.

a.Construct a99%

confidence interval for the population mean

.

Round your answers to two decimal places.

_____to______hours

b.Suppose the confidence interval obtained in partais too wide. Select all of the ways the width of this interval can be reduced.

-Lowering the confidence level

-Increasing the sample size

-Lowering the sample size

-Increasing the confidence level