# Question

According to Exercise 10.27, an insurance company wants to know if the average speed at which men drive cars is higher than that of women drivers. The company took a random sample of 27 cars driven by men on a highway and found the mean speed to be 72 miles per hour with a standard deviation of 2.2 miles per hour. Another sample of 18 cars driven by women on the same highway gave a mean speed of 68 miles per hour with a standard deviation of 2.5 miles per hour. Assume that the speeds at which all men and all women drive cars on this highway are both normally distributed with unequal population standard deviations.

a. Construct a 98% confidence interval for the difference between the mean speeds of cars driven by all men and all women on this highway.

b. Test at a 1% significance level whether the mean speed of cars driven by all men drivers on this highway is higher than that of cars driven by all women drivers.

c. Suppose that the sample standard deviations were 1.9 and 3.4 miles per hour, respectively. Redo parts a and b. Discuss any changes in the results.

a. Construct a 98% confidence interval for the difference between the mean speeds of cars driven by all men and all women on this highway.

b. Test at a 1% significance level whether the mean speed of cars driven by all men drivers on this highway is higher than that of cars driven by all women drivers.

c. Suppose that the sample standard deviations were 1.9 and 3.4 miles per hour, respectively. Redo parts a and b. Discuss any changes in the results.

## Answer to relevant Questions

Refer to Exercise 10.28. Now assume that the two populations are normally distributed with unequal and unknown population standard deviations. In Exercise 28 a. Make a 90% confidence interval for the difference between the ...Explain when would you use the paired-samples procedure to make confidence intervals and test hypotheses. Several retired bicycle racers are coaching a large group of young prospects. They randomly select seven of their riders to take part in a test of the effectiveness of a new dietary supplement that is supposed to increase ...Construct a 95% confidence interval for p̂1 – p̂2 for the following. n1 = 100, p̂1 = .81, n2 = 150, p̂2 = .77 Refer to the information given in Exercise 10.4. Test at a 5% significance level if µ1 is less than µ2. n1 = 650 1 = 1.05 σ1 = 5.22 n2 = 675 2 = 1.54 σ1 = 6.80Post your question

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