AP Stats Midterm

The following is a residual plot for a linear regression of y versus x.

B. A linear model is not appropriate.

The pulse rate for each person in a sample of 20 men and 20 women was recorded. The boxplots below summarize the pulse rates for the men and the women in the sample. Which of the following statements about the people in the sample must be true?

Not (A); (M): C. At least half of the women had higher pulse rates than three-fourths of the men.

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The following list shows the number of video games sold at a game store each day for one week. 15, 43, 50, 39, 22, 16, 20 Which of the following is the best classification of the data in the list?

D. Quantitative and discrete

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The table shows data that were collected from people who attended a certain high school basketball game and indicates the team each person rooted for and whether each of these people purchased food during the game. A person who attended the game will be selected at random. Which of the following correctly interprets mutually exclusive events represented by the table?

A. Rooting for the home team and rooting for the away team

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A candy company produces individually wrapped candies. The quality control manager for the company believes that the weight of the candies is approximately normally distributed with mean 720 milligrams (mg).If the manager's belief is correct, which of the following intervals of weights will contain the largest proportion of the candies in the distribution of weights?

B. 700 mg to 740 mg

The following table shows summary statistics for the number of hours a group of students spent playing video games last Monday and last Saturday. Based on the summary statistics, which of the following gives the best comparison of the range and the interquartile range (IQR)(IQR) of the two days?

B. The range and IQRIQR of hours played on Monday are both less than the range and IQRIQR of hours played on Saturday.

A set of bivariate data was used to create a least-squares regression line. Which of the following is minimized by the line?

B. The sum of the squared residuals

The combined percentage of key lime pies sold and pumpkin pies sold was less than 50%. Which of the following statements is not supported by the table?

C. For men, the number who chose a design with black was greater than the number who chose a design with blue.

A city planner is investigating traffic congestion at a certain intersection. To collect data, a camera will record the number of cars that pass through the intersection at different hours of the day and on different days of the week. Which of the following best describes the type of investigation being conducted by the city planner?

C. The investigation is an observational study because treatments are not imposed.

The following segmented bar chart shows the number of flights that were either on time or delayed at three different airports on one day. Which of the following statements is supported by the bar chart?

C. The number of on-time flights at Airport S is half the number of on-time flights at Airport T.

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The distribution of the number of transactions per day at a certain automated teller machine (ATM)(ATM) is approximately normal with a mean of 80 transactions and a standard deviation of 10 transactions. Which of the following represents the parameters of the distribution?

Not C; (C) D. μ=80;σ=10

An airline recorded the number of on-time arrivals for a sample of 100 flights each day. The boxplot below summarizes the recorded data for one year. Based on the boxplot, which of the following statements must be true?

E. The difference between the median and the lower quartile for the number of on-time arrivals is less than 2.

A randomized block design will be used in an experiment to compare two lotions that protect people from getting sunburned. Which of the following should guide the formation of the blocks?

Not E; (M): D. Participants within each block should be as similar as possible with respect to how easily they get sunburned. *(C) B. Participants should be randomly assigned to the blocks.

At a small coffee shop, the distribution of the number of seconds it takes for a cashier to process an order is approximately normal with mean 276 seconds and standard deviation 38 seconds. Which of the following is closest to the proportion of orders that are processed in less than 240 seconds?

Not C; (M): A. 0.17

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Which of the following can be used to show a cause-and-effect relationship between two variables?

B. A controlled experiment

Researchers will use a well-designed experiment to test the effectiveness of a new drug versus a placebo in relieving symptoms of the common cold. Which of the following will provide evidence that the new drug causes relief of symptoms?

D. The difference between the responses to the new drug and the placebo must be shown to be statistically significant to provide evidence that the new drug causes relief.

A scientist recorded the duration of the eruptions of the Old Faithful geyser in Yellowstone National Park that occurred during a one-month time period. The histogram below shows the distribution of the duration, in seconds, of the eruptions. Based on the histogram, which of the following is the best description of the distribution?

E. The distribution displays two clusters, with one cluster centered at about 125 seconds and the other centered at about 260 seconds, and has a range of at most 250 seconds.

For a random sample of 20 professional athletes, there is a strong, linear relationship between the number of hours they exercise per week and their resting heart rate. For the athletes in the sample, those who exercise more hours per week tend to have lower resting heart rates than those who exercise less. Which of the following is a reasonable value for the correlation between the number of hours athletes exercise per week and their resting heart rate?

Not A; (M): D. −0.87

The back-to-back stem-and-leaf plot below gives the percentage of students who dropped out of school at each of the 49 high schools in a large metropolitan school district. Which of the following statements is NOT justified by these data?

Not B; (M): D. The median drop-out rate of the 49 high schools decreased between the 1989-90 and 1992-1993 school years.

A middle school chess club has 5 members: Adam, Bradley, Carol, Dave, and Ella. Two students from the club will be selected at random to participate in the county chess tournament. What is the probability that Adam and Ella will be selected?

A. 1/20

The histogram above shows the number of minutes needed by 45 students to finish playing a computer game. Which of the following statements is correct?

B. The distribution is skewed to the left.

One student from a high school will be selected at random. Let A be the event that the selected student is a student athlete, and let B be the event that the selected student drives to school. IfP(A∩B)=0.08 and P(B|A)=0.25, what is the probability that the selected student will be a student athlete?

C. 0.32

Janelle collected data on the amount of time in minutes each person in a large sample of customers spent in a local store. The data also included recording the gender of each customer. These data were used to generate the boxplots shown below. Which of the following statements is true?

Not A; (M): E. Approximately half of the males in the sample of customers spent at least as much time in the store as any female in the sample of customers.

A certain type of remote-control car has a fully charged battery at the time of purchase. The distribution of running times of cars of this type, before they require recharging of the battery for the first time after its period of initial use, is approximately normal with a mean of 80 minutes and a standard deviation of 2.5 minutes. The shaded area in the figure below represents which of the following probabilities?

A. The probability that the running time of a randomly selected car of this type, before it requires recharging of the battery for the first time after its period of initial use, is between 75 minutes and 82.5 minutes.

Which of the following questions about cars in a school parking lot will allow for the collection of a set of categorical data?

E. What are the colors of the cars in the lot?

The boxplots above summarize two data sets, A and B. Which of the following must be true? I. Set A contains more data than Set B. II. The box of Set A contains more data than the box of Set B. III. The data in Set A have a larger range than the data in Set B.

Not E; (M): B. III only

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Which of the following does not describe a sampling method that has a potential source of voluntary response bias for the administration of a survey about college athletics at a university?

A. Giving the survey to 30 students selected at random from each of the eight dorms on campus

For which of the following distributions is the mean greater than the median?

A. Positively/Right Skewed

A sleep time of 15.9 hours per day for a newborn baby is at the 10th percentile of the distribution of sleep times for all newborn babies. Assuming the distribution is normal with standard deviation 0.5 hour, approximately what is the mean sleep time, in hours per day, for newborn babies?

D. 16.5

A restaurant manager collected data on the number of customers in a party in the restaurant and the time elapsed until the party left the restaurant. The manager computed a correlation of 0.78 between the two variables. What information does the correlation provide about the relationship between the number of customers in a party at the restaurant and the time elapsed until the party left the restaurant?

Not A; (M): C. The parties with a larger number of customers are associated with the longer times elapsed until the party left the restaurant.

Dairy farmers are aware there is often a linear relationship between the age, in years, of a dairy cow and the amount of milk produced, in gallons per week. The least-squares regression line produced from a random sample is Milkˆ=40.8−1.1(Age). Based on the model, what is the difference in predicted amounts of milk produced between a cow of 5 years and a cow of 10 years?

B. A cow of 5 years is predicted to produce 5.5 more gallons per week..

First-year students enrolled at a college were asked whether they play video games. The responses, classified by whether the students were enrolled in the school of sciences or the school of arts, are shown in the table. Of all the students enrolled in the school of arts who responded, approximately what proportion responded that they play video games?

C. 0.438

The following table summarizes the number of pies sold at a booth one day at a local farmers market. Which of the following statements is supported by the table?

E. The combined percentage of key lime pies sold and pumpkin pies sold was less than 50%.

A market research firm is studying the effects of price and type of packaging on sales of a particular product. Twenty-seven stores with shoppers of similar characteristics will be used in the study. The nine combinations of three price levels and three packaging types are the treatments of interest. Total sales of the product over a seven-week period will be recorded. Which of the following describes the best design to use for the study?

A. A completely randomized design. Randomly assign the nine combinations of price level and packaging type so that three stores use each combination.

Shalise competed in a jigsaw puzzle competition where participants are timed on how long they take to complete puzzles of various sizes. Shalise completed a small puzzle in 75 minutes and a large jigsaw puzzle in 140 minutes. For all participants, the distribution of completion time for the small puzzle was approximately normal with mean 60 minutes and standard deviation 15 minutes. The distribution of completion time for the large puzzle was approximately normal with mean 180 minutes and standard deviation 40 minutes. Approximately what percent of the participants had finishing times greater than Shalise's for each puzzle?

B. 16% on the small puzzle and 84% on the large puzzle

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The student government at a high school wants to conduct a survey of student opinion. It wants to begin with a simple random sample of 60 students. Which of the following survey methods will produce a simple random sample?

E. Number the students in the official school roster. Use a table of random numbers to choose 60 students from this roster for the survey. If not, it's C but that's stratified

Link

https://docs.google.com/document/d/1UgSjitiU7VmocfYxrzJ8tIWLBq7Jj-5XNK6MLbtSFi0/edit

The seniors at three high schools were surveyed about their plans after graduation. The following table shows the responses, classified by high school. One senior from the high schools will be selected at random. What is the probability that the senior selected will not be from High School B given that the senior responded with a choice other than college?

(C): C. 262/418

A dog food company wishes to test a new high-protein formula for puppy food to determine whether it promotes faster weight gain than the existing formula for that puppy food. Puppies participating in an experiment will be weighed at weaning (when they begin to eat puppy food) and will be weighed at one-month intervals for one year. In designing this experiment, the investigators wish to reduce the variability due to natural differences in puppy growth rates. Which of the following strategies is most appropriate for accomplishing this?

A. Block on dog breed and randomly assign puppies to existing and new formula groups within each breed.

The residual plots from five different least squares regression lines are shown below. Which of the plots provides the strongest evidence that its regression line is an appropriate model for the data and is consistent with the assumptions required for inference for regression?

C. Like a square

A certain county school district has 15 high schools. The high school seniors' plans after graduation in each school vary greatly from one school to the next. The county superintendent will select a sample of high school seniors from the district to survey about their plans after graduation. The superintendent will use a cluster sample with the high schools as clusters. A random sample of 5 high schools will be selected, and all seniors at those high schools will complete the survey. What is one disadvantage to selecting a cluster sample to investigate the superintendent's goal?

C. The schools in the cluster sample might not be representative of the population of seniors.

A program that was intended to cure a person's fear of spiders was offered at a local zoo. Volunteers with a fear of spiders participated in the program, which included holding a spider for 15 minutes. One month after they completed the program, the participants were contacted and surveyed about the program. Over 90 percent of the participants claimed they were cured of their fear of spiders. Based on the description of the program, which of the following statements is true?

D. Because the participants were self-selected, a person's desire to be cured could be a confounding variable.

A distribution of test scores is not symmetric. Which of the following is the best estimate of the z-score of the third quartile?

E. This z-score cannot be estimated from the information given.

A school is having a contest in which students guess the number of candies in a jar. The student whose guess is closest to the correct number of candies in the jar wins a prize. The number of candies guessed by male and female students is shown in the back-to-back stemplot below. Which of the following statements is true about the distributions of guesses?

D. The distributions of guesses for male and female students are both skewed to the left.

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A company determines the mean and standard deviation of the number of sick days taken by its employees in one year. Which of the following is the best description of the standard deviation?

A. Approximately the mean distance between the number of sick days taken by individual employees and the mean number of sick days taken by all employees

Each person in a random sample of adults was asked how many DVDs he or she owned. Summary statistics are given below. Which of the following statements is true?

D. The interquartile range of the number of DVDs owned is 65.

The investigation is an observational study because treatments are not imposed.

E. All women who are students at Midwestern colleges in the United States

A graduate student conducted a study of field mice in rural Kansas. The student obtained a sample of 100 field mice and recorded the weight, in grams, of each mouse. After the measurements were taken, it was discovered that the scale was not calibrated correctly. The student adjusted the 100 recorded measurements by subtracting 3 grams from each measurement. Which of the following statistics for the weight, in grams, of the field mice has the same value before and after the adjustment?

E. The interquartile range

The number of siblings was recorded for each student of a group of 80 students. Some summary statistics and a histogram displaying the results are shown below. An outlier is often defined as a number that is more than 1.5 times the interquartile range below the first quartile or above the third quartile. Using the definition of an outlier and the given information, which of the following can be concluded?

E. The median is less than the mean, and the distribution has two outliers.