Seat Belts A study of seat belt use involved children who were hospitalized after motor vehicle crashes. For a group of 123 children who were wearing seat belts, the number of days in intensive care units (ICU) has a mean of 0.83 and a standard deviation of 1.77. For a group of 290 children who were not wearing seat belts, the number of days spent in ICUs has a mean of 1.39 and a standard deviation of 3.06 (based on data from “Morbidity Among Pediatric Motor Vehicle Crash Victims: The Effectiveness of Seat Belts,” by Osberg and Di Scala. a. Use a 0.05 significance level to test the claim that children wearing seat belts have a lower mean length of time in an ICU than the mean for children not wearing seat belts. b. Construct a confidence interval appropriate for the hypothesis test in part (a). c. What important conclusion do the results suggest?

Choose the correct option and explain.

A bridal gown shop owner owns a store in San Francisco and a store in Redwood city. She is trying to figure out if clients tend to spend the same amount at both stores. She takes a random sample of 25 purchases from each store, and find the San Francisco store has a mean amount spent of $2500 with a standard deviation of $1500. The Redwood City store has a mean amount spent of $2000 with a standard deviation of $1000. Use a significance level of 10% to determine if the clients at the two stores spend the same amounts. State:  Plan: Do: Conclude:

In a study examining the relationship between socioeconomic status (SES) and academic achievement among high school students, the researchers collected data on 500 students from varying SES backgrounds. The SES was categorized into low, medium, and high. The academic achievement was measured using GPA scores. The following descriptive statistics were obtained: Mean GPA for low SES students: 2.8 Standard deviation of GPA for low SES students: 0.5 Mean GPA for medium SES students: 3.5 Standard deviation of GPA for medium SES students: 0.3 Mean GPA for high SES students: 4.0 Standard deviation of GPA for high SES students: 0.2 a) Calculate the coefficient of variation for each SES group and interpret the results.

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.

Fuel efficiency of Prius:  Fueleconomy.gov, the official US government source for fuel economy information, allows users to share gas mileage information on their vehicles. The histogram below shows the distribution of gas mileage in miles per gallon (MPG) from 14 users who drive a 2012 Toyota Prius. The sample mean is 53.3 MPG and the standard deviation is 5.2 MPG. Note that these data are user estimates and since the source data cannot be verified, the accuracy of these estimates are not guaranteed. (a) The EPA claims that a 2012 Prius gets 50 MPG (city and highway mileage combined). Do these data provide strong evidence against this estimate for drivers who participate on fueleconomy.gov? The test statistic is: __________________(please round to two decimal places)The p-value:___________________________ for this hypothesis test is:  (please round to four decimal places)(c) Please comment on the primary thing that is wrong about the following statement: There is sufficient evidence…

Entrance exam scores at Cititon University are normally distributed with a mean of 552 and a standard deviation of 29. If scholarships are awarded to the top 10% of scores, what is the minimum score needed to guarantee a scholarship?

A report about how American college students manage their finances includes data from a survey of college students. Each person in a representative sample of 793 college students was asked if they had one or more credit cards and if so, whether they paid their balance in full each month. There were 500 who paid in full each month. For this sample of 500 students, the sample mean credit card balance was reported to be $825. The sample standard deviation of the credit card balances for these 500 students was not reported, but for purposes of this exercise, suppose that it was $205. Is there convincing evidence that college students who pay their credit card balance in full each month have a mean balance that is lower than $907, the value reported for all college students with credit cards? Carry out a hypothesis test using a significance level of 0.01.   State the appropriate null and alternative hypotheses. H0: ? = 907 Ha: ? < 907 H0: ? = 907 Ha: ? > 907      H0: ? < 907…

In a certain country the heights of adult men are normally distributed with a mean of 67.2 inches and a standard deviation of 2.3 inches. The​ country's military requires that men have heights between 64 inches and 75 inches. Determine what percentage of this​ country's men are eligible for the military based on height.

A newspaper article reports that the mean cost for preventative dental care per year is $175 with a standard deviation of $35 (assume that this is the population standard deviation). You want to test whether the mean cost for preventative dental care in your company is different from what was reported in the article. You take a random sample of 250 employees and find the mean cost is $171. Does this signficantly differ from what was reported in the article? Run the appropriate test at α=0.05. Give each of the following to receive full credit: 1) the appropriate null and alternative hypotheses; 2) the appropriate test; 3) the decision rule; 4) the calculation of the test statistic; and 5) your conclusion including a comparison to alpha or the critical value. You MUST show your work to receive full credit. Partial credit is available.