1.A random sample of 45 sophomore students at an urban college indicated that they worked an average of 23.5 hours per week out of school. The standard deviation of their responses was 4.5 hours. The college claims that their students work an average of no more than 20 hours. Which of the following tests would be most appropriate in establishing that the school's estimate is low?

a right-tail t-test

a let-tail t-test

a left-tail z-test

a right-tail z-test

2.A random sample of81 cars traveling on Interstate Highway I-78produced a mean of 60 miles per hourand a standard deviation of 10 miles per hour.To construct a 95%confidence interval for the mean speed of the underlying population,which of the following is the correct critical value?

= 1.99, df = 80

= 1.671, df = 59

= 1.664,df= 80

= 2.000, df = 59