Fuel efficiency. Computers in some vehicles calculate various quantities related to performance. One of these is the fuel efficiency, or gas mileage, usually expressed as miles per gallon

(mpg). One of the authors of this book conducted an experiment with his Toyota Highlander Hybrid by randomly recording mpg readings shown on the vehicle computer while the car was set to 60 miles per hour by cruise control. Here are the mpg values from the experiment: DATADATA DATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATA DATADATADATADATADATA DATA FILE MILEAGE 37.2 21.0 17.4 24.9 27.0 36.9 38.8 35.3 32.3 23.9 19.0 26.1 25.8 41.4 34.4 32.5 25.3 26.5 28.2 22.1 Give a 95% confidence interval for μ, the mean mpg for this vehicle cruising at 60 miles per hour.
7.24 Testing the sticker information. Refer to the previous exercise. The vehicle sticker information for this Toyota Highlander Hybrid states a highway average of 27 mpg. Are the results of this experiment consistent with the vehicle sticker? Perform a significance test using the 0.05 significance level. Be sure to specify the hypotheses, your test statistic, the P-value, and your conclusion.
7.25 Bankruptcies in Canada. From 1980 to 1992, the number of company bankruptcies in Canada more than doubled. Dramatic improvements, however, have occurred since that time. By 2005, the number of bankruptcies had returned to where it was 25 years ago. One survey conducted by Statistics Canada, reported that the average number of bankruptcies per 1000 businesses from 1999 to 2005 was 8.98 with a standard error of 1.25.5 Construct a 95% confidence interval for the mean number of bankruptcies per 1000 businesses between 1999 and 2005.
7.26 Health insurance costs. The Consumer Expenditure Survey provides information on the buying habits of U.S. consumers.
6 In 2007, the average amount a household spent on health insurance was reported to be $1545. Assuming a sample standard deviation of $750 and sample size of n = 200, calculate a 90% confidence interval for the mean amount spent on health insurance.
7.27 Counts of seeds in one-pound scoops. A leading agricultural company must maintain strict control over the size, weight, and number of seeds they package for sale to customers. An SRS of 81 one-pound scoops of seeds was collected as part of a Six Sigma quality improvement effort within the company. The number of seeds in each scoop is shown below. DATADATA DATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATA DATADATADATADATADATA DATA FILE SEEDCOUNT 1471 1489 1475 1547 1497 1490 1889 1881 1877 1448 1503 1492 1553 1557 1504 1666 1717 1670 1703 1649 1649 1323 1311 1315 1469 1428 1471 1626 1658 1662 1517 1517 1519 1529 1549 1539 1858 1843 1857 1547 1470 1453 1412 1398 1398 1698 1692 1688 1435 1421 1428 1712 1722 1721 1426 1433 1422 1562 1583 1581 1720 1721 1743 1441 1434 1444 1500 1509 1521 1575 1548 1529 1735 1759 1745 1483 1464 1481 1900 1930 1953

(a) Create a histogram, boxplot, and a Normal quantile plot of these counts.

(b) Write a careful description of the distribution. Make sure to note any outliers and comment on the skewness or Normality of the data.

(c) Based on your observations in part (b), is it appropriate to analyze these data using the t procedures? Briefly explain your response.