‘ssfl ,onsider the table you used in question 22. Can you conclude that the mpg is less for tread B in for tread A? Use the a = 0.01 level and interpret in the context of the problem.
6 of 6
a random sample of 340 cars driven at low altitudes, 46 of them exceeded a standard of 10 grams of particulate pollution per gallon of fuel consumed. In an independent random sample of 85 cars driven at high altitudes, 21 of them exceeded the standard. Can you conclude that the proportion of high-altitude vehicles exceeding the standard is greater than the proportion of low-altitude vehicles exceeding the standard? Use the a = 0.05 level and Interpret in the context of the problem.
27) A statistics teacher claims that, on the average, 20% of her students get a grade of A, 35% get a B, 25% get a C, 10% get a D, and 10% get an F. The grades of a random sample of 100 students were recorded. The following table presents the results. State the null and alternate hypotheses. Compute the expected frequencies.
Grade A B CDF
Observed 29 42 20 5 4
5
28) The following table presents the numbers of employees, by age group, who were promoted, or not promoted, in a sample drawn from a certain industry during the past year. Can you conclude that the people in some age groups are more likely to be promoted than those in other age groups? Use the a = 0.05 level of significance.
Age
Under 30 30-39 40-49 50 and Over
Promoted 16 22 26 15
Not Promoted 38 39 45 38
29) How much noisier are streets where cars travel faster? A department of transportation worker wants to fit a simple linear regression model /41„ = + fl rx where x is the speed of the car in mph and y is the noise level in decibels. State the null and alternate hypothesis whether the speed of the car is significantly linearly associated with the noise level.
30) Using the same example from question 29, if we did the hypothesis test and got a p-value of 0.002. Interpret the p-value for determining whether ft exceeds 0.
31) Using the same example from question 29, the 95% confidence interval for the slope A is (0.16687,0.31162). Interpret this interval.
