ap stats review
27) Which of the following distributions has a mean of 60 and standard deviation of 4?
(A)
5) In population H, what is the height, to the nearest tenth of an inch, of the 70th percentile?
(A) 67.3 inches
35) Two antidepressants are to be compared in the treatment of elderly patients in a nursing home. Each patient has his or her own room, some with spectacular views of the ocean. The experimental design is to create homogeneous blocks with respect to window view. How should randomization be used for a randomized block design?
(A) Within each block, randomly pick half the patients to receive each antidepressant.
43) If P(A)=.25 and P(B)=.34, what is P(A∪B) if A and B are independent?
(B) .590
94) Given a set of ordered pairs (x, y) so that sx= 0.75 sy= 1.6 r= 0.55 What is the slope of the least-squares regression line for these data?
(B) 1.17
54) A residual:
(B) is how much an observed y-value differs from a predicted y-value.
40) What's the probability that a randomly selected marble will be blue or white?
(C) 0.50
108) A large bakery has many different products for sale. Suppose that 70% of all customers of the bakery order donuts, 50% order cinnamon rolls, and 40% order both. If a customer is randomly selected, what is the probability that they ordered either donuts or cinnamon rolls but not both?
(C) 40%
66) A set of data has a mean that is much larger than the median. Which of the following statements is most consistent with this information?
(C) The distribution is skewed right
81) A researcher is testing a company's new stain remover. He has contracted with 40 families who have agreed to test the product. He randomly assigns 20 families to the group that will use the new stain remover and 20 to the group that will use the company's current product. The most important reason for this random assignment is that
(C) randomization is a good way to create two groups of 20 families that are similar as possible, except for the treatments they receive.
57) Give, in millimeters, a minimum and maximum thickness that includes 68% of the population of bolts.
(D) 19.99 to 20.01 millimeters
7) To the nearest whole number, what percentile is associated with z = -0.68?
(D) 25th percentile
3) What are the categorical variables in your survey?
(D) Everything but average annual income and family size
47) Which of the following are true statements?
(D) I, II, and III
11) Which of the following can outliers affect significantly?
(D) I, III, and IV
2) Which of the variables you collect are continuous data?
(D) Only average annual income
79) Which of the following is correct?
(D) The coefficient of determination is the fraction of variability in y that can be explained by least-squares regression of y on x.
6) In population H, what is the z-score, to the nearest tenth, associated with the height 65 inches?
(D) z = -0.4
106) What is the size of the typical prediction error of this regression line?
(E) 30.16
46) Which of the following are true?
(E) I and III only
107) As part of a bear population study, data were gathered on a sample of black bears in the western United States to examie the relationship between the bear's neck girth ( distance around the neck) and the weight of the bear. Below is some of the output from a least-squares regression analysis examining the linear relationship between neck girth and weight. Which one of the following is the correct value and corresponing interpretation for the correlation coefficient?
(E) The correlation coefficient is 0.967. There is a stron positive linear relationship between a bear's neck girth and its weight.
10) An airline recorded the number of on-time arrivals for a sample of 100 flights each day. The boxplot below summarizes the records data for one year.
(E) The difference between the median and the lower quartile for the number of on-time arrivals is less than 2.
24) An AP Statistics teacher grades using z-scores. On the second major exam of the marking period, a student receives a grade with a z-score of -1.3. What is the correct interpretation of this grade?
(E) The student scored 1.3 standard deviations lower on the second exam than the class average on the second exam.
68) As part of a study on the relationship between the use of tanning booths and the occurrence of skin cancer, researchers reviewed the medical records of 1,436 people. The table below summarizes tanning booth use for people in the study who did and did not have skin cancer.
B) (190)/(896)
20) To which of the histograms below can the boxplot correspond?
MOST AT 50-60 AND 0-10
41) Find the probability of a randomly drawn marble being yellow, given that the marble is small.
(A) 0.39
58) Give, in millimeters, a minimum and a maximum thickness that will include 95% of the population of bolts.
(A) 19.98 to 20.02 millimeters
30) An advantage to using surveys as opposed to experiments is that
(A) 82
52) A study was conducted to evaluate the impact of taking a nutritional supplement on a person's reaction time. One hundred volunteers were placed into one of three groups according to their athletic ability: low, moderate, or high. Participants in each group were randomly assigned to take either the nutritional supplement or a placebo for six weeks. At the end of the six weeks, participants were given a coordination task. The reaction time in completing the task was recorded for each participant. The study compared the reaction times between those taking the supplement and those taking the placebo within each athletic ability level. Which of the following is the best description of the study?
(A) A randomized block design
8) Why is the IQR considered to be a resistant statistic?
(A) Adding a new extreme observation has little effect on it
78) 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.
96) Suppose that 30 percent of the subscribers to a cable television service watch the shopping channel at least once a week. You are to design a simulation to estimate the probability that none of five randomly selected subscribers watches the shopping channel at least once a week. Which of the following assignments of the digits 0 through 9 would be appropriate for modeling an individual subscriber's behavior in this simulation?
(A) Assign "0, 1, 2" as watching the shopping channel at least once a week and "3, 4, 5, 6, 7, 8, and 9" as not watching.
70) Control groups are used in experiments in order to ...
(A) Control the effects of lurking variables such as the placebo effect.
4) Given that the median is 270 and the interquartile range is 20, which of the following statements is true?
(A) Fifty percent of the data are greater than or equal to 270.
105) What is the least squares regression line for the information above?
(A) Size = -45713 + 23.983(Year)
101) The effect of removing the right-most point (near the positive x-axis) in the scatterplot shown would be:
(A) The slope of the LSRL will increase; r will increase
36) Which of the following statements is incorrect?
(A) Voluntary response samples often underrepresent people with strong opinions.
37) A critical difference between experiments and observational studies is
(A) an experiment often suggests a casual relationship, whereas an observational study only suggests an association.
56) Molly earned a score of 940 on a national achievement test. The mean test score was 850 with a standard deviation of 100. What proportion of students had a higher score than Molly? (Assume that test scores are normally distributed.)
(B) 0.18
17) Calculate the residual for a block with 10 streetlights and 1 crime a month.
(B) 0.6
42) Find the probability of a randomly drawn marble being large, given that the marble is black.
(B) 0.65
51) It is estimated that 20 percent of all drivers do not signal when changing lanes. In a random sample of four drivers, what is probability that at least one doesn't signal when changing lanes?
(B) 1-[(.8)]^4
73) A researcher interested in the age at which women have their first child surveyed a simple random sample of 250 women who have one child and found an approximately normal distribution with a mean age of 27.3 and a standard deviation of 5.4. According to the 68-95-99.7 rule, approximately 95% of women had their first child between the ages of
(B) 16.5 years and 38.1 years
74) The scores on a real estate licensing examination given in a particular state are normally distributed with a standard deviation of 70. What is the mean test score if 25% of the applicants scored above 475?
(B) 428
104) A linear regression was performed using the five following data points A(1, 11), B(5, 2), C(3, 7), D(7, 1), E(9, -2). The residual for which of the five points has the largest absolute value?
(B) B
77) Assume X and Y are events in the same sample space. If P(X) = 0.30 and P(Y) = 0.75 then which of the following inequalities must be true?
(B) I and III
14) In which of the following histograms is the mean less than the median?
(B) SKEW TO THE LEFT
49) Staff members of a high school newspaper want to obtain an estimate of the average number of years teachers in the state have been teaching. At an educational conference attended by many teachers in the state, the staff members randomly selected 50 conference attendees and asked the attendees how long they have been teaching. Which of the following describes the sample and the population to which it would be most reasonable for the staff members to generalize the results?
(B) The sample is the 50 conference attendees, and the population is all the conference attendees.
23) Which of the following is a true statement about the correlation coefficient r?
(B) The square of the correlation measures the proportion of the y-variance that is predictable from a knowledge of x.
99) A set of data relates the amount of annual salary raise and the performance rating. The least squares regression equation is where y is the estimated raise and x is the performance rating. Which of the following statements is not correct?
(B) This equation produces predicted raises with an average error of 0.
82) 100 volunteers who suffer from anxiety take part in a study. 50 are selected at random and assigned to receive a new drug that is thought to be extremely effective in reducing anxiety. The other 50 are given an existing anti-anxiety drug. A doctor evaluates anxiety levels after two months of treatment to determine if there has been a larger reduction in the anxiety levels of those who take the new drug. This would be double blind if
(B) neither the subjects nor the doctor knew which treatment any subject had received
75) The mean of a data set is 40 pounds and the standard deviation is 8 pounds. What value of an observation corresponds to a z-score of -1.25?
(C) 30
64) Using the empirical rule, you can assume that what percent of the normal distribution is outside two standard deviations of the mean in both directions?
(C) 5%
89) The weights of newborn baby boys have an approximately normal distribution with a mean of 8.0 pounds and a standard deviation of 1.5 pounds. A doctor tells a mother that her newborn baby boy has a weight at the 25th percentile. Which of the following is closest to this baby's weight?
(C) 7.00 pounds
12) Given these parallel boxplots, which of the following is incorrect?
(C) Both sets are skewed to both lower and higher values.
18) Using the regression equation above, correctly interpret the slope.
(C) For every additional streetlight per block, the crimes per month decrease by 0.2.
95) Lauren is enrolled in a very large college calculus class. On the first exam, the class mean was 75 and the standard deviation was 10, On the second exam, the class mean was 70 and the standard deviation was 15. Lauren scored 85 on both exams. Assuming the scores on each exam were approximately normally distributed, on which exam did Lauren score better relative to the rest of the class?
(C) She scored about equally well on both exams.
32) A company wishes to survey what people think about a new product it plans to market. They decide to randomly sample from their customer database as this includes phone numbers and addresses. This procedure is an example of which type of sampling?
(C) Simple random
63) Ms. Fisher wants to compare the effect of a new fertilizer on that of three older fertilizers - X, Y, and Z - on the growth of vegetables typically grown in small gardens. Two hundred green bean seedlings were individually planted in identical pots and randomly assigned to one of four groups of 50 each. Seedlings in one group were given the new fertilizer, and the three remaining groups of seedlings were given fertilizers X, Y, or Z, respectively. At the end of four weeks, all seedlings were dried and weighed. Ms. Fisher found that the mean weight of the seedlings in the group given the new fertilizer were significantly greater than the mean weights of seedlings in the other three groups. The scientists concluded that the new fertilizer was more effective than the other fertilizers for all vegetables. Why is Ms. Fisher's conclusion not appropriate?
(C) The experiment only included green beans, so the results cannot be generalized to all vegetables.
102) If the point labeled A is removed, which of the following statements would be true?
(C) The slope of the least squares regression line increases and the correlation coefficient increases.
80) Which of the following statements concerning residuals from a LSRL is true?
(C) The value of a residual is the observed value of the response minus the value of the response that one would predict from the least-squares regression line.
65) When drawing a histogram it is important to
(C) label the vertical axis so the reader can determine the counts or percents in each class interval.
67) If the standard deviation of a set is 0, you can conclude
(C) that all observations are the same value
53) The average noise level in a bar is 36 decibels with a standard deviation of 5 decibels. Assuming a normal distribution, what is the probability the noise level is between 30 and 40 decibels?
(D) 0.673
71) A sample of production records for an automobile manufacturer shows the following figures for production per shift:
(D) 50.00
90) The dotplot below displays the daily high temperature, in degrees Fahrenheit, for a city in the southeastern United States during the 28 days in the month of February 2014.
(D) 90
59) The SAT math scores for applicants to a particular engineering school are normally distributed with a mean of 680 and a standard deviation of 35. Suppose that only applicants with scores above 700 are considered for admission. What percentage of the applicants considered have scores below 750?
(D) 92.0 percent
76) In a statistics course, a linear regression equation was computed to predict the final exam score from the score on the first test. The equation was y = 10 + .9x where y is the final exam score and x is the score on the first test. Carla scored 95 on the first test. What is the predicted value of her score on the final exam?
(D) 95.5
38) Measurements of water quality were taken from a river downstream from an abandoned chemical dumpsite. Concentrations of a certain chemical were obtained from 9 measurements taken at the surface of the water, 9 measurements taken at mid-depth of the water, and 9 measurements taken at the bottom of the water. What type of study was conducted, and what is the response variable of the study?
(D) An observational study was conducted, and the response variable is the concentration of the chemical.
15) A random sample of golf scores gives the following summary statistics: n=20, x ̅=84.5, S_x=11.5, minX=68,Q_1=78,Med=86,Q_3=91,maxX=112. What can be said about the number of outliers?
(D) At least 1
13) Which of the following is true about the areas described under the normal curve?
(D) Fewer than one percent of the cases are located three standard deviations above or below the mean.
72) Halle takes three standardized tests. She scores 600 on all three. Using standardized scores (z-scores), rank her performance on the three tests from best to worst if the means and standard deviations of the tests are as follows:
(D) III, I, and II
39) A materials engineer wishes to compare the durability of two different types of paving material. She has 40 different one-mile stretches of interstate highway that she's been authorized to repave for this study. She decides to carry out a matched pairs experiment. Which of the following is the best way for her to carry out the randomization for this study?
(D) Let each of the 40 roadways act as its own pair, dividing each roadway into the first half-mile and the second half-mile. Flip a coin for each of the 40 roadways to decide which half-mile gets which pavement.
44) An auto analyst is conducting a satisfaction survey, sampling from a list of 10,000 new car buyers. The list includes 2,500 Ford buyers, 2,500 GM buyers, 2,500 Honda buyers, and 2,500 Toyota buyers. The analyst selects a sample of 400 car buyers, by randomly sampling 100 buyers of each brand.
(D) No, because every possible 400-buyer sample did not have an equal chance of being chosen.
34) A bank wishes to survey its customers. The decision is made to randomly pick ten customers who just have checking accounts, ten customers who just have savings accounts, and ten customers who have both checking and savings accounts. This procedure is an example of which type of sampling?
(D) Stratified
16) How many crimes a month are predicted when there are 7 streetlights on a block?
(E) 1.0
29) A national achievement test is administered annually to 3rd graders. The test has a mean score of 100 and a standard deviation of 15. If Jane's z-score is 1.20, what was her score on the test?
(E) 118
28) Suppose the scores on an exam have a mean of 75 with a standard deviation of 8. If one student has a test result with a z-score of -1.5, and a second student has a test result with a z-score of 2.0, how many points higher was the second student's result than that of the first?
(E) 28
100) The following numbers appear in a table of random digits: 38683 50279 38224 09844 13578 12708 24684
(E) 38, 35, 02, 22, 40
62) Rainwater was collected in water collectors at 30 different sites near an industrial complex and the amount of acidity (pH level) was measured. The data ranged from pH 2.6 to pH 6.3. The following stemplot of the data was constructed
(E) E
21) A study is conducted relating AP Statistics exam scores to the total number of study hours for the AP Statistics class put in by students during the academic year, and the correlation is found to be .6, which of the following is a true statement?
(E) Higher exam scores tend to be associated with higher numbers of study hours.
33) The back-to-back stemplot on the right shows the number of books read in a year by a random sample of college and high school students. Which of the following statements are true?
(E) I, II, and III
48) A national consumer magazine reported the following correlations.
(E) I, II, and III
1) A scientist recorded the duration of the eruption 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.
(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.