Statistics 201 Practice Exam 3 From Fall 2014 This practice exam is provided solely for the purpose of familiarizing you with the format and style of the Stat 201 exams There is no explicit or implicit guarantee that the upcoming exam will ask similar questions If you use the practice exam as your only tool to help you prepare for the upcoming exam you most likely will not do well on the exam You should still do the things you would have done if you did not have access to this practice exam such as re read the text go over your class notes re work the online homework problems and look at the list of exam topics provided and make sure that you understand all the concepts listed within it 1 EXAM GRADE 2 1 The regional manager of a grocery store chain is concerned that there may be a significant difference between two of the stores she manages regarding the average time it takes employees to check out customers wanting to pay for their items The cash registers used at these stores automatically keep track of the start and end time of each transaction as well as a total transaction time for each transaction in seconds Rather than look at all transactions she decided to take a random sample from both stores over the last month to produce two different columns of data one for STORE A and one for STORE B An example of the data she gathered is below along with some other output from JMP for the two stores There were 44 transactions for STORE A and 41 transactions for STORE B in the data set In any one month each store processes about 15 000 transactions The manager wants to know is there a statistically significant difference between the average transaction time of these two stores i 3 points Let A the population average transaction time for STORE A and B the population average transaction time for STORE B Using proper mathematical notation write out the null and alternative hypotheses this regional manager wishes to test 3 Question 1 continued ii 3 points There are four conditions that must be met for a t test to be a valid technique for comparing two means Name three of them indicate whether or not you think each condition is met and briefly explain your YES or NO selection Condition 1 is Is this condition met Circle one YES NO Now briefly explain your choice Condition 2 is Is this condition met Circle one YES NO Now briefly explain your choice Condition 3 is Is this condition met Circle one YES NO Now briefly explain your choice 4 Question 1 continued iii 2 points Below is the t test output from JMP for these data Based on the hypotheses you specified in part i what is the p value for the manager s hypothesis test Fill in the blank below p value iv 2 points Based on the output above which store had a higher sample average transaction time Circle one STORE A STORE B Now briefly explain how you know which store had the higher sample average v 2 points If we use 0 10 what is your conclusion regarding the manager s hypothesis test Circle one REJECT Ho FAIL TO REJECT Ho Now briefly explain why you circled the answer you did providing numerical details if appropriate vi 3 points Your answer to part v above reject or fail to reject Ho is not a complete conclusion for the manager s hypothesis test although it is a start State the remainder of the conclusion in the context of this problem 5 2 Many consumer groups feel that Canada s drug approval process is too easy and as a result too many drugs are approved that are later found to be unsafe On the other hand a number of industry lobbyists have pushed for a more lenient approval process so that pharmaceutical companies can get new drugs approved more easily and quickly Assume that the null hypothesis is that a new unapproved drug is unsafe and that the alternative hypothesis is that a new unapproved drug is safe i 3 points Explain the risks of committing a Type I error in the context of the problem ii 3 points Explain the risks of committing a Type II error in the context of the problem iii 2 points Which type of error are the consumer groups trying to avoid Briefly explain 6 3 Below is some output for a 2 sample t test Assume all the necessary conditions have been met for the t test to be valid i 3 points The value of the t Ratio has been erased Use other values in the output to help you calculate the missing t Ratio value Report your answer to 3 decimal places ii 3 points The values for the 95 confidence interval have also been erased Based on other values in the output which option below must be the correct confidence interval In the notation below assume Standing represents GROUP 1 and Sitting represents GROUP 2 Circle the correct answer NOTE you are not expected to actually calculate the confidence interval nor can you without technology from just the information given a b c d e f 4 3102 1 2 2 7778 1 1637 1 2 1 0157 0 8146 1 2 2 9941 0 6132 1 2 2 4413 1 0367 1 2 1 1427 2 6673 1 2 4 6639 7 4 A large insurance company tracks life expectancy information to assist in determining the cost of life insurance premiums The insurance company knows that last year the average life expectancy of its policyholders was 77 years The company will change its premium structure if there is evidence that people who buy their policies are living longer on average than before The company randomly samples 100 recently paid policies in other words policies the company has had to pay death benefits on The average life span in the sample of 100 policies is 78 32 years and the sample standard deviation is 4 2729 years i 3 points Assume that the conditions to perform a hypothesis test have been met State the null and alternative hypothesis the insurance company will test ii 3 points Calculate the appropriate test statistic iii 2 points Circle the p value in the output below that corresponds to the hypotheses you wtrote in part i Test Statistic Prob t Prob t Prob t t Test 0 0025 0 0013 0 9987 iv 3 points Using 05 do these sample data indicate that the insurance company should change its premiums because the average life expectancy of its policy holders has increased Briefly explain 8 5 A UT student decides to analyze the relationship between Greek Life and Family Economic Level The JMP output ON THE NEXT PAGE shows his analysis of the data which was taken from a survey given to Spring Semester 2014 Stat 201 students The Greek Life variable indicates whether or not the student was in a sorority or fraternity Family Economic Level has three classifications Assume …
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