AP Stats Semester 1 2017-2018 Finals Review

A: Randomization is a good way to create two groups of 20 intersections that are as similar as possible, so that comparisons can be made between the two groups

A civil engineer is testing the reliability of traffic signal controllers produced by two different companies. He has 20 sets of controllers from each company, and he has been given clearance to install them at 40 different intersections in the city. He randomly assigns the controllers from company A to 20 intersections and the controllers from company B to the other intersections. The most important reason for this random assignment is that a. randomization is a good way to create two groups of 20 intersections that are as similar as possible, so that comparisons can be made between the two groups. b. randomization eliminates the impact of any confounding variables. c. randomization makes the analysis easier since the data can be collected and entered into the computer in any order. d. randomization ensures that the study is double-blind. e. randomization reduces the impact of outliers.

E: The college should hire a new statistician

A community college announces that the correlation between college entrance exam grades and scholastic achievement was found to be -1.08. On the basis of this you would tell the college that a. the entrance exam is a good predictor of success. b. the exam is a poor predictor of success. c. students who do best on this exam will be poor students. d. students at this school are underachieving. e. the college should hire a new statistician.

C: 75%

A medical researcher collects health data on many women in each of several countries. One of the variables measured for each woman in the study is her weight in pounds. The following list gives the five-number summary for the weights of adult women in one of the countries. Country A: 92, 110, 120, 160, 240 About what percent of Country A women weigh between 110 and 240 pounds? a. 50% b. 65% c. 75% d. 85% e. 95%

E: If the mean performance rating is 1.2, then the mean raise is $3800

A set of data describes the relationship between the size of annual salary raises and the performance ratings for employees of a certain company. The least squares regression equation is y8 = 1400 + 2000x where y is the raise amount (in dollars) and x is the performance rating. Which of the following statements must be true? a. For each one-point increase in performance rating, the raise will increase on average by $1400. b. The actual relationship between salary raises and performance rating is linear. c. The residuals for half the observations in the dataset will be positive. d. The correlation between salary raise and performance rating is negative. e. If the mean performance rating is 1.2, then the mean raise is $3800.

B: The mean would increase by $5,000 and the median would not change

A small company that prints custom t-shirts has 6 employees, one of whom is the owner and manager. Suppose the owner makes $120,000 per year and the other employees make between $40,000 and $50,000 per year. One day, the owner decides to give himself a $30,000 raise. Which of the following describes how the company's mean and median salaries would change? a. The mean and median would both increase by $5,000. b. The mean would increase by $5,000 and the median would not change. c. The mean would increase by $6,000 and the median would not change. d. The median would increase by $6,000 and the mean would not change. e. The mean would increase by $6,000, but we cannot determine the change in the median without more information.

C: Other variables may be confounded with variable X. For example, states with large populations may have both larger numbers of people who don't complete high school and more infant deaths

According to the 1990 census, those states with an above-average number of people X, who fail to complete high school tend to have an above average number of infant deaths, Y. In other words, there is a positive association between X and Y. The most plausible explanation for this is a. X causes Y. Programs to keep teens in school will help reduce the number of infant deaths. b. Y causes X. Programs that reduce infant deaths will ultimately reduce high school dropouts. c. Other variables may be confounded with variable X. For example, states with large populations may have both larger numbers of people who don't complete high school and more infant deaths. d. Both of these variables are directly affected by the higher incidence of cancer in certain states. e. The association between X and Y is purely coincidental.

C: Cluster sample

An airline that wants to assess customer satisfaction chooses a random sample of 10 of its flights during a single month and asks all of the passengers on those flights to fill out a survey. This is an example of a a. multistage sample. b. stratified sample. c. cluster sample. d. simple random sample. e. convenience sample.

B: We can determine whether the new drug reduces symptoms more than the old drug for the subjects in the study

Eighty volunteers who currently use a certain brand of over-the-counter allergy medication have been recruited to participate in a trial of a new allergy medication. The volunteers are randomly assigned to one of two groups. One group continues to take their current medication, the other group switches to the new experimental medication. Each is asked after two weeks if their allergy symptoms are worse, better, or about the same as they were at the start of the study. Which of the follow best describes a conclusion that can be drawn from this study? a. We can determine whether the new drug reduces symptoms more than the old drug for anyone who suffers from allergies. b. We can determine whether the new drug reduces symptoms more than the old drug for the subjects in the study. c. We can determine whether the allergies sufferers' symptoms improved more with the new drug than with the old drug, but we can't establish cause and effect. d. We cannot draw any conclusions, since the all the volunteers were already taking the old drug when the experiment started. e. We cannot draw any conclusions, because there was no control group

B: 2.47

For children between the ages of 18 months and 29 months, there is an approximately linear relationship between height and age. The relationship can be represented by y8= 64.93 + 0.63x, where y represents height (in centimeters) and x represents age (in months). Loretta is 20 months old and is 80 centimeters tall. What is her residual? a. -2.47 b. 2.47 c. -12.60 d. 12.60 e. 77.53

D: 79.11

For children between the ages of 18 months and 29 months, there is an approximately linear relationship between height and age. The relationship can be represented by y8= 64.93 + 0.63x, where y represents height (in centimeters) and x represents age (in months). Joseph is 22.5 months old. What is his predicted height? a. 50.80 b. 64.96 c. 65.96 d. 79.11 e. 87.40

B: 09, 10, 11, 12, 13, and 14

Here are the IQ test scores of 10 randomly chosen fifth-grade students: 145 139 126 122 125 130 96 110 118 118 To make a stemplot of these scores, you would use as stems a. 0 and 1 b. 09, 10, 11, 12, 13, and 14 c. 96, 110, 118, 122, 126, 130, 139, and 145 d. 0, 2, 3, 4, 6, 8, and 9 e. None of the above is a correct answer.

C: The mean must be greater than the median

If a distribution is skewed to the right, which of the following is true? a. The mean must be less than the median. b. The mean and median must be equal. c. The mean must be greater than the median. d. The mean is either equal to or less than the median, e. It's impossible to tell which of the above statements is true without seeing the data.

D: There was insufficient attention to the placebo effect

In an experiment to measure the effect of fluoride "varnish" on the incidence of tooth cavities, 34 10-year-old-girls whose parents volunteered them for the study were randomly assigned to two groups. One group was given fluoride varnish annually for 4 years along with a standard dental hygiene regimen; the other group only followed the standard dental hygiene regimen. The mean number of cavities in the two groups was compared at the end of the treatments. Which of the following is a problem with this experiment? a. Since the subjects were not randomly selected for the study, we cannot conclude that a reduction in cavities can be attributed to the fluoride treatment. b. There was no control group. c. The absence of replication increases the impact of random variation. d. There was insufficient attention to the placebo effect. e. The experimental subjects should not have been limited to girls.

A: Gas mileage is a response variable, and you expect to find a negative association

Other things being equal, larger automobile engines are less fuel-efficient. You are planning an experiment to study the effect of engine size (in liters) on the fuel efficiency (in miles per gallon) of sport utility vehicles. In this study, a. gas mileage is a response variable, and you expect to find a negative association. b. gas mileage is a response variable, and you expect to find a positive association. c. gas mileage is an explanatory variable, and you expect to find a strong negative association. d. gas mileage is an explanatory variable, and you expect to find a strong positive association. e. gas mileage is an explanatory variable, and you expect to find very little association.

C: Unchanged: equal to 0.52

The correlation between the heights of fathers and the heights of their (fully grown) sons is r = 0.52. This value was based on both variables being measured in inches. If fathers' heights were measured in feet (one foot equals 12 inches), and sons' heights were measured in furlongs (one furlong equals 7920 inches), the correlation between heights of fathers and heights of sons would be a. much smaller than 0.52 b. slightly smaller than 0.52 c. unchanged: equal to 0.52 d. slightly larger than 0.52 e. much larger than 0.52

E: Her sample is 38, 35, 02, 22, 40

The following numbers appear in a table of random digits: 38683 50279 38224 09844 13578 28251 12708 24684 A scientist will be measuring the total amount of leaf litter in a random sample (n = 5) of forest sites selected without replacement from a population of 45 sites. The sites are labeled 01, 02, . . . , 45 and she starts at the beginning of the line of random digits and takes consecutive pairs of digits. Which of the following is correct? a. Her sample is 38, 25, 02, 38, 22 b. Her sample is 38, 68, 35, 02, 22 c. Her sample is 38, 35, 27, 28, 08 d. Her sample is 38, 65, 35, 02, 79 e. Her sample is 38, 35, 02, 22, 40

B: 63 inches to 73 inches

The heights of American men aged 18 to 24 are approximately Normally distributed with a mean of 68 inches and a standard deviation of 2.5 inches. Only about 5% of young men have heights outside the range a. 65.5 inches to 70.5 inches b. 63 inches to 73 inches c. 60.5 inches to 75.5 inches d. 58 inches to 78 inches e. none of the above

D: The distance between the weight of each infant born in April and the mean weight was, on average about 10.2 oz

The mean birth weight of infants born at a certain hospital in the month of April was 128 oz. with a standard deviation of 10.2 oz. Which of the following is a correct interpretation of standard deviation? a. All the infants born in April weighed between 117.8 oz. and 138.2 oz. b. About half the infants born in April weighed between 117.8 oz. and 138.2 oz c. The difference between the mean weight and the median weight of infants born in April was 10.2 oz. d. The distance between the weight of each infant born in April and the mean weight was, on average, about 10.2 oz. e. The mean weight of infants born in subsequent months is likely to be within 10.2 oz. of the mean weight in April.

A: It could be any number between 64 and 68 miles per hour

The mean speed of vehicles in the "cars only" lanes of the New Jersey turnpike is 68 miles per hour. The mean speed of vehicles in the "any vehicle" lanes is 64 miles per hour. What must be true about the mean speed of all vehicles on the turnpike, assuming these are the only types of lanes? a. It could be any number between 64 and 68 miles per hour. b. It must be larger than the median speed. c. It must be larger than 66 miles per hour. d. It must be 66 miles per hours. e. We don't have enough information to draw any conclusion about the mean speed of all vehicles.

B: A matched pairs experiment

To test the effects of a new fertilizer, 100 plots were divided in half. Fertilizer A is randomly applied to one half, and B to the other. This is a. an observational study. b. a matched pairs experiment c. a completely randomized experiment. d. a block design, but not a matched pairs experiment. e. impossible to classify unless more details of the study are provided.

B: An uncontrolled experiment

What electrical changes occur in muscles as they get tired? Student subjects are instructed to hold their arms above their shoulders as long as they can. Meanwhile, the electrical activity in their arm muscles is measured. This is a. an observational study b. an uncontrolled experiment. c. a randomized comparative experiment. d. a matched pairs design. e. impossible to describe unless more details of the study are provided.

C: I and II only

Which of the following properties is true for all Normal density curves? I. They are symmetric. II. The curve reaches its peak at the mean. III. 95% percent of the area under the curve is within one standard deviation of the mean. a. I only b. II only c. I and II only d. I and III only e. All three statements are correct.

A: Nonresponse can cause bias in surveys because nonrespondents may behave differently than people who respond

Which of the following statements is true? a. Nonresponse can cause bias in surveys because nonrespondents may behave differently than people who respond. b. Bias arising from undercoverage can be compensated for by increasing sample size. c. Stratified random sample is often employed to reduce the impact of response bias. d. People's responses to survey questions tend not to be influenced by the age, race, or sex of the interviewer. e. Sophisticated statistical methods can always correct the results if the population you are sampling from is different from the population of interest, for example, due to under coverage

C: A block design

You work for an advertising agency that is preparing a new television commercial to appeal to women. You have been asked to design an experiment to compare the effectiveness of three versions of the commercial. Each subject will be shown one of the three versions and then asked her attitude toward the product. You think there may be large differences between women who are employed outside the home and those who are not. Because of these differences, you should use a. a completely randomized design. b. a categorical variable. c. a block design. d. stratified design e. a multistage sample.