STAT 100 Midterm 1 Sample Exam - Spring 2013 QUESTION 1 (6 pts) 3417 people were recently selected at random from all adult taxpayers in Canada and answered questions about the Canada Revenue Agency (CRA) assessments. A. (1 pt) What was the population for the study? B. One question was, “Do you feel that CRA assessments are accurate?” 2137 answered “Yes”. a. (1 pt) Estimate the percentage of the population that feels that the CRA assessments are accurate. b. (1 pt) Find the margin of error for the estimate. c. (1 pt) Explain what the margin of error tells you about the population here. C. (2 pts) Suppose that three years ago another survey of about the same size asked the same question and got an estimate that was statistically significantly lower than the current estimate. Between that survey and this one, CRA began a new program to improve their assessment accuracy. Can they claim that the new program has been successful? Explain. STAT 100 Midterm 1 – Sample Exam QUESTION 2 (4 pts) The table at right lists the number of grouse sighted by a wildlife manager at a certain wildlife park over 5 years. He would like to try to figure out whether the different ages (Adult or Immature) and genders (Female and Male) have any effect on the number of sightings. A. List any response variables: B. List any explanatory variables: C. Select any variable and list its values: Year 1993 1993 1993 1993 1994 1994 1994 1994 1995 1995 1995 1995 1996 1996 1996 1996 1997 1997 1997 1997 1998 1998 1998 1998 Age I I F F I I F F I I F F I I F F I I A A I I A A Gender M F F M M F F M M F F M M F F M M F F M M F F M Sightings 103 99 139 85 145 168 298 122 68 93 205 87 105 148 171 69 147 169 175 95 110 119 150 87 QUESTION 3 (2 pts) Below are some measurements and corresponding instruments for each one indicate whether it is likely to be a valid measurement (in the blank, respond YES for valid, NO for not valid or MAYBE for not enough information) A. Using movie rating (G, PG, 14A, 18A, R) to measure the appropriateness of a film for children B. Using length of a movie as a measure of its quality C. Using an x-ray as a measure of the presence of a fracture D. Using a written driver’s test as a measure of driving ability 2 STAT 100 Midterm 1 – Sample Exam QUESTION 4 (6 pts) Please indicate the correct answer from A. Which of the following is not true of a simple random sample of size 1000 chosen from a population of size 4,000,000? a) Every individual in the population has the same chance of selection as every other individual. b) Every set of 1000 individuals has the same chance of being the sample as every other set of 1000 individuals. c) Every individual of the population has chance 1 in 1000 of being included in the sample. d) Every set of 500 individuals has the same chance of being included in the sample as every other set of 500 individuals. B. Bias in a sampling method is a. any error in the sample result, that is, any deviation of the sample result from the truth about the population. b. the random error due to using chance to select a sample. c. any error due to practical difficulties such as contacting the subjects selected. d. any systematic error that tends to occur in the same direction every time you use this sampling method. e. racism or sexism on the part of those who take the sample. C. A sportswriter wants to know how strongly Columbus, Ohio residents support building a new stadium for the local minor league baseball team, the Columbus Clippers. She stands outside the stadium before a game and interviews the first 25 people who enter the stadium. The newspaper asks you to comment on their survey of local opinion. You say a. this is a simple random sample. It gives very accurate results. b. this is a simple random sample. The results are not biased, but the sample is so small that variation will be high. c. this is a census, because all fans had a chance to be asked. It gives very accurate results. d. the sampling method is biased. It will almost certainly overestimate the level of support among all Columbus, Ohio residents. e. the sampling method is biased. It will almost certainly underestimate the level of support among all Columbus, Ohio residents. 3 STAT 100 Midterm 1 – Sample Exam QUESTION 5 (6 pts) A study was performed on the effects of distractions on studying. A room at a university was set up with a sound system and a TV. Student volunteers who entered the room were exposed to either (1) loud rock music, (2) soft baroque music, (3) an adventure movie on the TV, or (4) quiet (no TV or music). The student volunteers first took a brief pre-test. The students were placed into groups according to scores on the pre-test: the top 4 formed the first group, the next 4 highest formed the second group, and so on. There were 20 volunteers, so there were 5 groups. From each group, one student was exposed to the loud rock, one to the soft baroque, one to the TV, and one to the quiet. Every student was given some materials to read and study for an hour. At the end of the hour, each student took a final test on the materials. A. (1 pt) What kind of study is this? a. an observational study b. an experiment c. a census d. a survey e. None of the above B. (1 pt) What is the response variable? a. the type of distraction b. the final test score c. the pre-test score d. the room e. none of the above C. (1 pt) What purpose does the pre-test serve? a. it is the response variable b. it is used to create blocks c. it is the treatment variable d. it is the randomization device e. none of the above D. (1 pt) The test that students took after the study period was a. a block b. an instrument c. a randomization d. a census e. none of the above 4 STAT 100 Midterm 1 – Sample Exam QUESTION 5 Cont’d E. (1 pt) The population for this study is: a. Monkeys b. Students at the same university c. Adults d. All university students e. None of the above F. (1 pt) Suppose that the average final test score in among students exposed to loud rock was statistically significantly lower than the average among students who listened to soft baroque. Which of the following conclusions can be made? a. b. c. d. e. Modern music is more distracting than classical music Rock music is more distracting than baroque music Any kind of music is distracting None the study is fundamentally flawed None of the above QUESTION 6 (3 pts) Dinehere.ca is a website devoted to customer ratings for restaurants in the lower mainland. People can create a username on the site using an e-mail address and password, and then can rate restaurants and real others’ ratings. Restaurants are scored on a 1-5 scale in 4 separate areas: Food, Service, Value, and Ambiance. The rater’s Overall score for a restaurant is calculated automatically from the average of these 4 areas’ scores. Restaurants are then rated on the basis of the average Overall score across all raters. A username may rate each restaurant only once (only the username’s most recent review counts toward the restaurant’s average). A. (1 pt) What method of data collection is this? B. (2 pts) Comment on the general quality and reliability of a restaurant’s rating, indicating any problems you see that may arise. 5 STAT 100 Midterm 1 – Sample Exam QUESTION 7 (5 pts) A. (2 pts) If a study is conducted ethically, which of the following are true? (Choose all that apply). a. The researchers use randomization to select participants b. The researchers will not release the names of individuals who participated in the study c. The researchers use margins of error to report results d. Subjects are given a choice whether to participate B. (1 pt) Why use a placebo in an experiment? (Choose one) a. It helps to keep patients from getting sick b. It helps to estimate how much response the other treatments are actually causing c. It helps to prevent bias by the researcher d. It helps to keep the experiment more random e. All of the above f. None of the above C. (1 pt) If an experiment is not blinded, what should you be worried about? (Choose one) a. Subjects in one treatment group may be inherently quite different from subjects in other treatment groups. b. The comparisons of different treatment groups may not be very accurate c. The comparisons of different treatments’ effects may not be very precise d. The responses may not be kept confidential e. All of the above f. None of the above D. (1 pt) Prescription drug safety trials are (almost) always conducted on a sample of adult male volunteers. This is a problem when the time comes to prescribe the drugs to the general public because (Choose one) a. There are not enough adult males left to take the drugs who haven’t already been exposed to them b. The samples are too small for the results to apply to the general public c. We can’t be sure that women and children will react to the drugs the same way that the adult males did d. All of the above e. None of the above 6