A car-rental company is interested in the amount of time its vehicles are out of operation for repair work. State all assumptions and find a 98% confidence interval for the mean number of days in a year that all vehicles in the company's fleet are out of operation if a random sample of 10 cars showed the following number of days that each had been inoperative. 19 18 17 13 30 11 10 24 State all assumptions. Select all the assumptions below. A. The sample comes from a normal population B. The sample size is at least 30 C. It is a random sample D. The variance is less than the mean 22 5 Find a 98% confidence interval for the population mean. The 98% confidence interval is from a lower limit of to an upper limit (Round to two decimal places as needed.) Q

Assume that samples have been randomly selected from normally distributed populations.The table below shows the weights of 9 subjects before and after following a particular diet for two months. Subject A B C D E F G H I Before 169 180 157 133 202 124 190 210 181 After 162 178 145 125 181 126 182 195 163 Construct a 99% confidence interval for the mean difference of the "before" minus "after" weights. Interpret the results.

A professor wants to know whether or not there is a difference in comprehension of a lab assignment among students depending on if the instructions are given all in text, or if they are given primarily with visual illustrations. She randomly divides her class into two groups of 15, gives one group instructions in text and the second group instructions with visual illustrations. The following data summarizes the scores the students received on a test given after the lab. Let the populations be normally distributed with a population standard deviation of 5.32 points for both the text and visual illustrations. Text (Group 1) Visual Illustrations (Group 2) 57.3 59 45.3 57.6 87.1 72.9 61.2 83.2 43.1 64 87.3 76.7 75.2 78.2 88.2 64.4 67.5 89 86.2 72.9 67.2 88.2 54.4 43.8 93 97.1 89.2 95.1 52 84.1 Is there evidence to suggest that a difference exists in the comprehension of the lab based on the…

Tina catches a 14-pound bass.  She does not know the population mean or standard deviation.  So she takes a sample of five friends and they say the last bass they caught was 9, 12, 13, 10, and 10 pounds.  Find the t and calculate a 95% (α = .05) confidence interval.