Question

1) At a traffic stop on a Saturday night 34% of 98 drivers were intoxicated. What is the 99% confidence interval for the population proportion of drunk drivers? Give your answers as decimals, to two places.

2) You measure 42 textbooks' weights, and find they have a mean weight of 58 ounces. Assume the population standard deviation is 2.8 ounces. Based on this, construct a 90% confidence interval for the true population mean textbook weight.

Give your answers as decimals, to two places

Answer 1

1)

99% confidence interval for p is

- Z/2 * sqrt [ ( 1 - ) / n ] < p < + Z/2 * sqrt [ ( 1 - ) / n ]

0.34 - 2.5758 * sqrt [ 0.34 * ( 1 - 0.34) / 98] < p < 0.34 + 2.5758 * sqrt [ 0.34 * ( 1 - 0.34) / 98]

0.22 < p < 0.46

99% CI is ( 0.22 , 0.46 )