Suppose that the average number of miles that a car is driven in the first three years is 41,500. To determine whether leased cars are driven more than “ average”, 25 leased cars were sampled and the average number of miles on the leased cars was 43,780 with a standard deviation of 10,520. To determine whether the average number of miles on leased cars is statistically significantly greater than the number of miles on other cars (using the 10% level of

Assume the average amount of caffeine consumed daily by adults is normally distributed with a mean of 260 mg and a standard deviation of 48 mg. In a random sample of 600 ​adults, how many consume at least 320 mg of caffeine​ daily?

Is it worth pursuing a doctoral degree in education if you already have an undergraduate degree? One way to help make this decision is to look at the mean incomes of these two groups. Suppose that 15 people with bachelor’s degrees in education were surveyed. Their mean annual salary was $⁢31,500 with a standard deviation of $⁢7900. Seventeen people with doctoral degrees in education were found to have a mean annual salary of $⁢47,500 with a standard deviation of $⁢6900. Assume that the population variances are not the same. Construct a 99% confidence interval to estimate the true difference between the mean salaries for people with doctoral degrees and undergraduate degrees in education. Let Population 1 be the salaries for people with doctoral degrees and Population 2 be the salaries for people with undergraduate degrees. Round the endpoints of the interval to the nearest whole number, if necessary.

1. The fuel efficiency of a new model pick-up truck (truck) is measured in miles per gallon (mpg). A company claims that their new truck gets 25 mpg on average. A consumer group thinks the company is lying and claims that the mean mileage for all the trucks is less than 25 mpg. In a random sample, of forty-five of these trucks the mean mpg was 23.3 mpg with a standard deviation of 5.1 mpg. a. Conduct a hypothesis test to test the consumer group's claim at the 5% significance level. Be sure to state you Ho and Ha, your test statistic and p- value, whether or not you reject Ho and whether you support the claim. b. Write a complete sentence describing what a Type I error is in context. c. Write a complete sentence describing what a Type II error is in context.