Stat Review
A distribution in N(25,5). According to the Empirical Rule, approximately what percent of the data would you expect to lie between 20 and 25? (A) 30% (B) 34% (C) 60% (D) 68% (E) 95%
B
All but one of these statements contain a mistake. Which could be true? (A) The correlation between a football player's weight and the position he plays is 0.54. (B) The correlation between the amount of fertilizer used and the yield of beans is 0.42. (C) The correlation between a car's length and its fuel efficiency is 0.71 miles per gallon. (D) There is a high correlation (1.09) between height of a corn stalk and its age in weeks. (E) There is a correlation of 0.63 between gender and political party.
B
If X is normally distributed with a mean of 50 and a standard deviation of 8, which of the following is NOT a correct way to find the probability that X > 45? (A) P (X > 45) = P (z>45-508) = P (z>-.63) (B) P (X > 45) = P (z>50-458) = P (z>-.63) (C) P (X > 45) = 1- P (X < 45) (D) P (X > 45) = 1- P (X ≤ 45) (E) All of these are correct
B
Predict the number of students taking the AP Statistics exam in 2015. a. 18,643,250 students; this prediction is not reliable because it is too large and AP Statistics cannot possibly grow that fast. b. 18,643,250 students; this prediction is reliable. c. 180,250 students; this prediction is reliable. d. 180,250 students; this prediction is not reliable because it is extrapolation. e. 180 students; this prediction is not reliable because it is extrapolation.
d
What is the probability P(X=2 | Y=3), that is, the probability that a student has an average television usage given the he never exercises? A .10 B .17 C .22 D .40 E .60
d
What is the probability that a randomly selected student has a GPA between 2.0 and 3.0? A .025 B .227 C .450 D .475 E .506
d
When would the use of a placebo be recommended in an experiment? a. When there are sufficient resources to warrant the use of a placebo b. If the existing treatment is one that the researcher doesn't want to be included in the study c. If the placebo can be used with animals for the appearance of an alternate treatment d. When there isn't an existing treatment and you want to be sure the subjects feel they are being treated e. To make sure the placebo works before using it on other studies
d
Which is true about sampling? I. An attempt to take a census will always result in less bias than sampling. II. Sampling error is usually reduced when the sample size is larger. III. Sampling error is the result of random variations and is always present. a. I only b. II only c. III only d. II and III e. all three
d
Which is true of the data shown in the histogram? I. The distribution is skewed to the right. II. The mean is probably smaller than the median. III. We should use median and IQR to summarize these data. a. I only b. II only c. III only d. II and III only e. I, II, and III
d
Which of the following are important in the designs of experiments? I Control of confounding variables. II Randomization in assigning subjects to different treatments. III Replication of the experiment using sufficient numbers of subjects. A I and II B I and III C II and III D I, II, and III E None of the above gives the complete set of true responses.
d
Which of the following are true statements? I The area under a normal curve is always equal to 1, no matter what the mean and standard deviation are. II The smaller the standard deviation of a normal curve, the higher and narrower the graph. III Normal curves with different means are centered around different numbers A I and II B I and III C II and III D I, II, and III E None of the above gives the complete set of true responses.
d
Which of the following are true statements? I. In an experiment some treatment is intentionally forced on one group to note the response. II. In an observational study information is gathered on an already existing situation. III. Sample surveys are observational studies, not experiments. a. I and II b. I and III c. II and III d. I, II, and III e. None of the above gives the complete set of true responses.
d
With regard to a particular gene, the percentages of genotypes AA, Aa and aa in a particular population are, respectively, 60%, 30% and 10%. Furthermore, the percentages of these genotypes that contract a certain disease are, respectively, 1%, 5% and 20%. If a person does contract the disease, what is the probability that the person is the genotype AA? A .006 B .010 C .041 D .146 E .600
d
The five-number summary of credit hours for 24 students in a statistics class is: Min - 13 Q1 - 15 Median - 16.5 Q3 - 18 Max - 22 Which statement is true? a. There are no outliers in the data. b. There is at least one low outlier in the data. c. There is at least one high outlier in the data. d. There are both low and high outliers in the data. e. None of the above.
a
What is the false-positive rate? That is, what is the probability of testing positive given that the person does not have HIV? A .054 B .050 C .130 D .417 E .875
a
What is the predictive value of the test? That is, what is the probability that a person has HIV and tests positive? A .070 B .130 C .538 D .583 E .875
a
What is the probability P(X=2, Y=3), that is, the probability that a student has an average television usage but never exercises? A .10 B .1125 C .22 D .40 E .60
a
What is the probability that a randomly selected student has a GPA under 2.0 and has skipped many classes? A. .080 B. .281 C. .285 D .314 E .727
a
Which of the following are true statements? I In general, strong association implies causation. II In well-designed well-conducted experiments, strong association implies causation. III Causation and association are unrelated concepts. a I only b II only c III only d I and II e I, II, and III
b
Which is true of the data shown in the histogram? The distribution is approximately symmetric. The mean and median are approximately equal. The median and IQR summarize the data better than the mean and standard deviation. (A) I only (B) III only (C) I and II (D) I and III (E) I, II, and III
c
Which of the following are true statements? I By the Law of Large Numbers, the mean of a random variable will get closer and closer to a specific value. II The standard deviation of a random variable is never negative. III The standard deviation of a random variable is 0 only if the random variable takes on a lone single value. A I and II B I and III C II and III D I, II and III E None of the above gives the complete set of true responses
c
Which of the following is false? a. This is a very good model, but since the residual plot shows a distinct pattern there is a more appropriate model in existence. b. It is reasonable to use the LSRL as a predictor for years 1997-2010. c. The model over estimates the number of students taking the AP Statistics exam in 2007. d. The data point corresponding to 1997 is an outlier. e. The correlation coefficient indicates that the linear relationship between number of students taking the AP Statistics exam and year is strong and positive.
c
Which of the following is the correct interpretation of the slope of the LSRL? a. Every 9.25 years, an average of one thousand more students take the AP Statistics exam. b. For each consecutive year, an average of 9,250 more students take the AP Statistics exam. c. Every year, 9,250 more students take the AP Statistics exam. d. For each consecutive year, an average of 4,500 more students take the AP Statistics exam. e. Every 4.5 years, an average of one thousand more students take the AP Statistics exam.
c
Which of the following is the correct interpretation of the y-intercept of the LSRL? a. The first AP Statistics exam (in 1997) had 7,500 students taking it. b. The first AP Statistics exam (in 1997) had 4,500 students taking it. c. The first AP Statistics exam (in 1997) is predicted to have had 4,500 students taking it. d. The first AP Statistics exam (in 1997) is predicted to have had 7,500 students taking it. e. The first AP Statistics exam (in 1997) is predicted to have had 9,250 students taking it.
c
Which of the following statements are true? I. Stem and leaf plots are useful both for quantitative and categorical data sets. II. Stem and leaf plots are equally useful for small and very large data sets III. Stem and leaf plots can show symmetry, gaps, clusters and outliers. a. I only b. II only c. III only d. I and II e. I and III
c
Which of the following summaries are changed by adding a constant to each data value? I. the mean II. the median III. the standard deviation a. I only b. III only c. I and II d. I and III e. I, II, and III
c
Which of the following variables would most likely follow a Normal model? (A) family income (B) heights of singers in a co-ed choir (C) weights of adult male elephants (D) scores on an easy test (E) all of these
c
Are X and Y independent? A Yes, because the conditional probabilities P(X=x | Y=y) equal the corresponding unconditional probability P(X=x). B Yes, because the joint probabilities are equal to the product of the respective probabilities. C Yes, because of either of the above answers D No. E The answer cannot be determined from the given information.
d
Double-blinding in experiments is important so that I. The evaluators do not know which treatment group the participants are in. II. The participants do not know which treatment group they are in. III. No one knows which treatment any of the participants is getting. a. I only b. II only c. III only d. I and II e. I, II, and III
d
If 75% of all families spend more than $75 weekly for food, while 15% spend more than $150, what is the mean weekly expenditure and what is the standard deviation? A μ = 83.33, σ = 12.44 B μ = 56.26, σ = 11.85 C μ = 118.52, σ = 56.26 D μ = 104.39, σ = 43.86 E μ = 139.45, σ = 83.33
d
If the point in the upper left corner of the scatterplot is removed, what will happen to the correlation (r) and the slope of the line of best fit (b)? a. They will not change. b. Both will increase. c. Both will decrease. d. r will increase and b will decrease. e. r will decrease and b will increase.
d
A coffee machine can be adjusted to deliver any fixed number of ounces of coffee. If the machine has a standard deviation in delivery equal to 0.4 ounce, what should be a mean setting to that an 8-ounce cup will overflow only 0.5% of the time? A 6.97 ounces B 7.22 ounces C 7.34 ounces D 7.80 ounces E 9.03 ounces
a
A factory dumps an average of 2.43 tons of pollutants into a river every week. If the standard deviation is 0.88 tons, what is the probability that in a week more than 3 tons are dumped? A .2578 B .2843 C .6500 D .7157 E .7422
a
A nutritionist believes that having each player take a vitamin pill before a game enhances the performance of the football team. During the course of one season, each player takes a vitamin pill before each game, and the team achieves a winning season for the first time in several years. Is this an experiment or an observational study? A An experiment, but with no reasonable conclusion possible about cause and effect. B An experiment, thus making cause and effect a reasonable conclusion. C An observational study, because there was no use of a control group. D An observational study, but a poorly designed one because randomization was not used. E An observational study, thus allowing a reasonable conclusion of association but not of cause and effect.
a
A television game show has three payoffs with each of the probabilities: Payoff ($): 0 1,000 10,000 Probability: .6 .3 .1 What are the mean and standard deviation for the fine variable? A μx=1,300 and σx=2, 934 B μx=1, 300 and σx=8, 802 C μx=3, 667 and σx=4, 497 D μx=3, 667 and σx=5, 508 E None of the above gives a set of correct answers.
a
Are "GPA between 2.0 and 3.0" and "skipped few classes" independent? A No, because .475 ≠ .506. B No, because .475 ≠ .890. C No, because .450 ≠ .475. D Yes, because of conditional probabilities. E Yes, because of the product rule.
a
Based on the scatterplot to the right, which of the following is true? a. Point A is an outlier and an influential point. b. Point A is an outlier but not an influential point. c. Point A is not an outlier but is an influential point. d. Point A is not an outlier nor an influential point. e. None of these are true.
a
Cucumber grown on a certain farm have weights with standard deviation of 2 ounces. What is the mean weight if 85%of the cucumbers weigh less than 16 ounces? A 13.92 B 14.30 C 14.40 D 14.88 E 15.70
a
If we wish to compare the average PSAT scores of boys and girls taking AP Statistics at this high school, which would be the best way to gather these data? a. Census b. SRS c. stratified sample d. observational study e. experiment
a
In November 1994, Intel announced that a "subtle flaw" in its Premium chip would affect 1 in 9 billion division problems. Suppose a computer performs 20 million divisions (a not unreasonable number) in the course of a particular program. What is the probability of no error? Of at least one error? A .99778; .00222 B .000000000111; .00222 C .000000000111; .999999999889 D .999999999889; .000000000111 E .999999999889; .00222
a
In a 1974 "Dear Abby" letter a woman lamented that she had just given birth to her eighth child, and all were girls! Her doctor had assured her that the chance of her eighth child being a girl was only 1 in 100. a. Given that having a girl is equally likely to having a boy, what was the real probability that the eighth child would be a girl? b Before the birth of the first child, what was the probability that the woman would give birth to eight girls in a row? (A) .5; .0039 (C) .5;.5 (E) .5; .01 (B) .0039; .0039 (D) .0039; .4
a
In an experiment, the primary purpose of blinding is to reduce ... a. bias. b. confounding. c. randomness. d. undercoverage. e. variation.
a
Jay Olshansky from the University of Chicago was quoted in Chance News as arguing that for average life expectancy to reach 100, 18% of the people would have to live to 120. What standard deviation is he assuming for this statement to make sense? A 21.7 B 24.4 C 25.2 D 35.0 E 111.1
a
Last weekend police ticketed 18 men whose mean speed was 72 miles per hour, and 30 women going an average of 64 mph. Overall, what was the mean speed of all the people ticketed? (A) 67 mph (B) 68 mph (C) 69 mph (D) none of these (E) It cannot be determined.
a
The SPCA collects the following data about the dogs they house. Which is categorical? (A) breed (B) age (C) weight (D) number of days housed (E) veterinary costs
a
The correlation between x and y is 0.84. What is the correlation between 3x + 4 and 5 - y? a. 0.84 b. 0.48 c. -.084 d. -.048 e. cannot be determined without the original data
a
When using midterm exam scores to predict a student's final grade in a class, the student would prefer to have a a. positive residual, because that means the student's final grade is higher than we would predict with the model. b. positive residual, because that means the student's final grade is lower than we would predict with the model. c. residual equal to zero, because that means the student's final grade is exactly what we would predict with the model. d. negative residual, because that means the student's final grade is lower than we would predict with the model. e. negative residual, because that means the student's final grade is higher than we would predict with the model.
a
Which of the following are true statements? I. In an experiment researchers decide how people are placed in different groups. II. In an observational study, the participants select which groups they are in. III. A control group is most often a self-selected grouping in an experiment. a. I and II b. I and III c. II and III d. I, II, and III e. None of the above gives the complex set of true responses.
a
Which of the following is not required in an experimental design? a. blocking b. control c. randomization d. replication e. all are required in an experimental design.
a
Your Stats teacher tells you your test score was the 3rd quartile for the class. Which is true? I. You got 75% on the test. II. You can't really tell what this means without knowing the standard deviation. III. You can't really tell what this means unless the class distribution is nearly Normal. (A) none of these (B) I only (C) II only (D) III only (E) II and III
a
A company sponsoring a new Internet search engine wants to collect data on the ease of using it. Which is the best way to collect the data? a. census b. sample survey c. observational study d. experiment e. simulation
b
Variables are considered to be confounded if a. they are both studied as part of the experiment b. their effects on the response variable cannot be separated c. more than on additional treatment group is included in the experiment d. the response variable is controlled by a placebo e. randomization wasn't used in setting up the initial experimental study
b
A basketball player has a 70% free throw percentage. Which plan could be used to simulate the number of free throws she will make in her next five free throw attempts? I. Let 0,1 represent making the first shot, 2, 3 represent making the second shot,..., 8, 9 represent making the fifth shot. Generate five random numbers 0-9, ignoring repeats. II. Let 0,1,2 represent missing a shot and 3,4,...,9 represent making a shot.. Generate five random numbers 0-9 and count how many numbers are in 3-9. III. Let 0, 1, 2 represent missing a shot and 3, 4,..., 9 represent making a shot. Generate five random numbers 0-9 and count how many numbers are in 3-9, ignoring repeats. a. I only b. II only c. III only d. II and III e. I, II, and III
b
A statistics teacher decides to compare this year's students to all those she has taught over the history of the course. She will use the students' examination performances as the method of comparison. Which of the following is true in this context? a. The mean performance of this year's students is a parameter. b. The mean performance of this year's students is a statistic. c. The mean of all except this year's students is a parameter. d. The mean of all students is a statistic. e. None of these are true.
b
A trucking firm determines that its fleet of trucks averages a mean of 12.4 miles per gallon with a standard deviation of 1.2 miles per gallon on cross-country hauls. What is the probability that one of the trucks averages fewer than 10 miles per gallon? A .0082 B .0228 C .4772 D .5228 E .9772
b
Consider the following Which of the following statements are true? I. Total sales in 1995 were two times the total sales in 1994, while total sales in 1996 were three times the 1994 sales. II. The choice of labeling the vertical axis results in a misleading sales picture. III. A histogram showing the same information, but this time with a vertical axis starting at $78,000 would be misleading. a. I only b. II only c. III only d. II and III e. None of these gives the complete set of true responses.
b
Following are the SAT math scores for an AP Statistics class of 20 students: 664, 658, 610, 670, 640, 643, 675, 650, 676, 575, 660, 661, 520, 667, 668, 635, 671, 673, 645, and 650. The distribution of scores is a. symmetric b. skewed to the left c. skewed to the right d. uniform e. bell-shaped
b
Given the following Minitab printout, which of the following is false? a. 80% of the variability in y is explained by the linear association created with x. b. Since r = 0.898, the linear association between x and y is strong and positive. c. As x increases by one unit, y decreases, on average, 1.6914 units. d. When x is zero units, y is predicted to be -0.868. e. The equation of the LSRL is y=-0.868- 1.6914x .
b
Given the probabilities P(A) = .4 and P(A ∪ B)= .6, what is the probability P(B) if A and B are mutually exclusive? If A and B are independent? A .2; .4 B .2; .33 C .33; .2 D .6; .33 E .6; .4
b
If probabilities P(A)= .2 and P(B)= .1, what is P(A∪B) if A and B are independent? A .02 B .28 C .30 D .32 E There is insufficient information to answer this question.
b
In a 1927-32 Western Electric Company study on the effect of lighting on worker productivity, productivity increased with each increase in lighting but then also increased with each decrease in lighting. If it is assumed that the workers knew a study was in progress, this is an example of a. the effect of a treatment unit. b. the placebo effect. c. the control group effect. d. sampling error. e. voluntary response bias.
b
Of A-D, which is not a critical part of designing a good experiment? a. Control of known sources of variability. b. Random selection of subjects. c. Random assignment of subjects to treatments. d. Replication of the on a sufficient number of subjects. e. All of these are important.
b
School administrators collect data on students attending the school. Which of the following variables is quantitative? (A) class (freshman, soph., junior, senior) (B) grade point average (C) whether the student is in AP classes (D) whether the student has taken the SAT (E) none of these
b
Suppose X and Y are random variables with E(X) = 500, VAR(X)= 50, E(Y) = 400, and VAR(Y)= 30. Given that X and Y are independent, what are the expected value and variance of the random variable X - Y? A E(X-Y) = 100, VAR(X-Y) = 20 B E(X-Y) = 100, VAR(X-Y) = 80 C E(X-Y) = 900, VAR(X-Y) = 20 D E(X-Y) = 900, VAR(X-Y) = 80 E There is insufficient information to answer this question.
b
Suppose X and Y are random variables with μX = 10, σX = 3, μY =1 5, σY = 4. Given that X and Y are independent, what are the mean and standard deviation of the random variable X + Y? A μx+Y=25 and σx+Y=3.5 B μx+Y=25 and σx+Y=5 C μx+Y=25 and σx+Y=7 D μx+Y=12.5 and σx+Y=7 E There is insufficient information to answer this question.
b
Suppose that 60% of students who take the AP Statistics exam score 4 or 5, 25% score a 3, and the rest score a 2 or 1. Suppose further that 95% of those scoring 4 or 5 receive college credit, 50% of those scoring 3 receive such credit, and 4% of those scoring 1 or 2 receive credit. If a student chosen at random from among those taking the exam receives college credit, what is the probability that she scored a 3 on the exam? A .125 B .178 C .701 D .813 E .822
b
Suppose that a Normal model described student scores in a history class. Parker has a standardized score (z-score) of +2.5. This means that Parker a. is 2.5 points above average for the class. b. is 2.5 standard deviations above average for the class. c. has a standard deviation of 2.5. d. has a score that is 2.5 times the average for the class. e. None of the above.
b
The SPCA has kept these data records for the past 20 years. If they want to show the trend in the number of dogs they have housed, what kind of plot should they make? (A) boxplot (B) timeplot (C) bar graph (D) pie chart (E) histogram
b
The mean income per household in a certain state is $9500 with a standard deviation of $1750. The middle 95% of incomes are between what two values? A $5422 and $13578 B $6070 and $12,930 C $6621 and $12,379 D $7260 and $11,740 E $8049 and $10,951
b
The mean score of a college placement exam is 500 with a standard deviation of 100. Ninety-five percent of the test takers score above what? A 260 B 336 C 405 D 414 E 664
b
The owner of a car dealership planned to develop strategies to increase sales. He hoped to learn the reasons why many people who visit his car lot do not eventually buy a car from him. For one month he asked his sales staff to keep a list of the names and addresses of everyone who came in to test drive a car. At the end of the month he sent surveys to the people who did not buy the car, asking them why. About one third of them returned the survey, with 44% of those indicating that they found a lower price elsewhere. Which is true? I. The population of interest is all potential car buyers. II. This survey design suffered from non-response bias. III. Because it comes from a sample 44% is a parameter, not a statistic. a. I only b. II only c. I and II only d. II and III only e. I, II, and III
b
What is the probability that a student from this class eats breakfast but does not floss their teeth? (A) 9% (B) 11% (C) 34% (D) 57% (E) 91%
b
Which of the following is the correct interpretation of the coefficient of determination? a. 99.8% of the variability in the number of students taking the AP Statistics exam is explained by the linear relationship with year. b. 99.6% of the variability in the number of students taking the AP Statistics exam is explained by the linear relationship with year. c. 99.8% of the variability in year is explained by the linear relationship with the number of students taking the AP Statistics exam. d. 99.6% of the variability in year is explained by the linear relationship with the number of students taking the AP Statistics exam. e. The linear relationship between the number of students taking the AP Statistics exam and year is strong and positive.
b
Which of the following scatterplots could have created the following residual plot? (A) (B) (C) (D) (E)
b
The veterinary bills for the dogs are summarized In the ogive shown. Estimate the IQR of these Expenses. (A) $50 (D) $150 (B) $75 (E) $200 (C) $100
c
Two sections of a class took the same quiz. Section A had 15 students who had a mean score of 80, and Section B had 20 students who had a mean score of 90. Overall, what was the approximate mean score for all of the students on the quiz? (A) 84.3 (B) 85.0 (C) 85.7 (D) none of these (E) It cannot be determined.
c
What is the probability distribution for X? A P(X=1) = .05, P(X=2) = .2, P(X=3) = .15 B P(X=1) = .10, P(X=2) = .2, P(X=3) = .15 C P(X=1) = .20, P(X=2) = .2, P(X=3) = .15 D P(X=1) = .40, P(X=2) = .2, P(X=3) = .15 E It cannot be determined from the given information.
c
What is the probability that a randomly selected student has a GPA under 2.0 or has skipped many classes? A .080 B .281 C .285 D .314 E .727
c
When the estrogen-blocking drug tamoxifen was first introduced to treat breast cancer, there was a concern that it would cause osteoporosis as a side effect. To test this concern, cancer subjects were randomly selected and given tamoxifen, and their bone density was measured before and after treatment. Which of the following is a true statement? I. This study was an observational study. II This study was a sample survey of randomly selected cancer patients. III This study was an experiment in which the subjects were used as their own controls. a I only b II only c. III only d I and III e None of the above gives the complete set of true response.
c
A correlation of zero between two quantitative variables means that a. we have done something wrong in our calculation of r. b. there is no association between the two variables. c. there is no linear association between the two variables. d. re-expressing the data will guarantee a linear association between the two variables. e. None of the above.
c
A residuals plot is useful because I. it will help us to see whether our model is appropriate. II. it might show a pattern in the data that was hard to see in the original scatterplot. III. it will clearly identify influential points. (A) I only (B) II only ( C) I and II only (D) I and III only (E) I, II, and III
c
Companies proved to have violated pollution laws are being fined various amounts with the following probabilities: Fine ($): 1000 10,000 50,000 100,000 Probability: .4 .3 .2 .1 What are the mean and standard deviation for the fine variable? A μx=40,250 and σx=39,118 B μx=40,250 and σx=45,169 C μx=23,400 and σx=31,350 D μx=23,400 and σx=85,185 E None of the above gives a set of correct answers.
c
If we want to discuss any gaps and clusters in a data set, which of the following should not be chosen to display the data set? a. histogram b. stem-and-leaf plot c. boxplot d. dotplot e. any of these would work
c
In the previous problem, suppose that the researchers suspected that women over the age of 55 may respond differently to the treatment. Given that a random sample of 40,000 women over the age of 45 has already been chosen, the study would have been improved by a. a stratified sample, with strata determined by age. b. a stratified sample, with strata determined by gender. c. a block design, with blocks determined by age. d. a block design, with blocks determined by gender. e. a double-blind completely randomized designed.
c
More dogs are being diagnosed with thyroid problems than have been diagnosed in the past. A researcher identified 50 puppies without thyroid problems and kept records of their diets for several years to see if any developed thyroid problems. This is a(n) a. randomized experiment b. survey c. prospective study d. retrospective study e. blocked experiment
c
Placebos are a tool for a. sampling b. blocking c. blinding d. control e. randomization
c
Residuals are . . . a. possible models not explored by the researcher. b. variation in the data that is explained by the model. c. the difference between observed responses and values predicted by the model. d. data collected from individuals that is not consistent with the rest of the group. e. none of these.
c
Suppose the average height of a policeman is 71 inches with a standard deviation of 4 inches, while the average height of a police woman is 66 inches with a standard deviation of 3 inches. If a committee looks at all the ways of paring up one male with one female office, what will the mean and standard deviation for the different in heights for the set of possible partners. A Mean of 5 inches with a standard deviation of 1 inch. B Mean of 5 inches with a standard deviation of 3.5 inches. C Mean of 5 inches with a standard deviation of 5 inches. D Mean of 68.5 inches with a standard deviation of 1 inch. E Mean of 68.5 inches with a standard deviation of 3.5 inches.
c
Suppose your local school district decides to randomly test high school students for attention deficit disorder (ADD). There are three high schools in the district, each with grades 9-12. The school board pools all of the students together and randomly samples 250 students. Is this a simple random sample? a. Yes, because the students were chosen at random. b. Yes, because each student is equally likely to be chosen. c. Yes, because they could have chosen any 250 students from throughout the district. d. No, because we can't guarantee that there are students from each school in the sample. e. No, because we can't guarantee that there are students from each grade in the sample.
c
The best estimate of the standard deviation of the mens' weights displayed in this dotplot is (A) 10 (B) 15 (C) 20 (D) 25 (E) 40
c
The correlation coefficient between high school grade point average (GPA) and college GPA is 0.560. For a student with a high school GPA that is 2.5 standard deviations above the mean, we would expect that student to have a college GPA that is ____ the mean. a. equal to b. 0.56 SD above c 1.4 SD above d. 2.5 SD above e. None of these are correct
c
A chemistry professor who teaches a large lecture class surveys his students who attend his class about how he can make the class more interesting, hoping he can get more students to attend. This survey method suffers from a. voluntary response bias b. nonresponse bias c. response bias d. undercoverage e. None of the above
d
A customer product agency tests miles per gallon for a sample of automobiles using each of four octanes of gasoline. Which of the following is true? a There are four explanatory variables and one response variable. b There is one explanatory variable and four levels of response. c Miles per gallon is the only explanatory variable, but there are four response variables corresponding to the different octanes. d There are four levels of a single explanatory variable. e Each explanatory level has an associated level of response.
d
A professor has kept records on grades that students have earned in his class. If he wants to examine the percentage of students earning the grades A, B, C, D, and F during the most recent term, which kind of plot could he make? (A) boxplot (B) timeplot (C) dotplot (D) pie chart (E) histogram
d
A regression analysis of students' college grade point averages (GPAs) and their high school GPAs found R2 = 0.311. Which of these is true? I. High school GPA accounts for II. 31.1% of college GPA. II. 31.1% of college GPAs can be correctly predicted with this model. III. 31.1% of the variance in college GPA can be accounted for by the model. A) I only B) II only C) I and II D) III only E) None
d
A researcher wants to compare the performance of three types of pain relievers in volunteers suffering from arthritis. Because people of different ages may suffer arthritis of varying degrees of severity, the subjects are split into two groups: under 60 and over 60. Subjects in each group are randomly assigned to take one of the medications. Twenty minutes later they rate their levels of pain. This experiment ... a. is completely randomized. b. uses matched pairs. c. has two factors, medication and age. d. has one factor (medication) blocked by age. e. has one factor (age) blocked by medication type.
d
A study of which candidate city residents planned to vote for in an upcoming election would be considered biased if a. individuals were selected randomly to participate from a list of city registered voters b. every 50th person on a registered voters list was contacted and asked to identify who they would vote for in the upcoming election c. individuals selected to participate from the city list of registered voters were first separated by gender and a percent of males and females based on their percentage in the voter pool, were randomly selected d. the participants selected from a list of registered voters were contacted via telephone e. two clusters of registered voters from neighborhoods were chosen and the entire cluster was surveyed where one cluster was of an urban section and the other suburban section of the voter base
d
A researcher wants to compare the effect of a new type of shampoo on hair condition. The researcher believes that men and women may react to the shampoo differently. Additionally, the researcher believes that the shampoo will react differently on hair that is dyed. The subjects are split into four groups: men who dye their hair; men who do not dye their hair; women who dye their hair; women who do not dye their hair. Subjects in each group are randomly assigned to the new shampoo and the old shampoo. This experiment a. is completely randomized. b. has three factors (shampoo type, gender, whether hair is dyed). c. has two factors (gender and whether hair is dyed) blocked by shampoo type. d. has two factors (shampoo type and whether hair is dyed) blocked by gender e. has one factor (shampoo type), blocked by gender and whether hair is dyed.
e
An electronic product takes an average of 3.4 hours to move through an assembly line. If the standard deviation is 0.5 hour, what is the probability that an item will take between 3 and 4 hours? A .2119 B .2295 C .3270 D .3811 E .6730
e
An inspection procedure at a manufacturing plant involves picking three items at random and then accepting the whole lot if at least two of the three items are in perfect condition. If in reality 90% of the whole lot are perfect, what is the probability that the whole lot will be accepted? A .600 B .667 C .729 D .810 E .972
e
Does donating blood lower cholesterol levels? 50 volunteers have a cholesterol test, then donate blood, and then have another cholesterol test. Which aspect of experimental design is present? a. randomization b. a control group c. a placebo d. blinding e. none of these
e
Given that 52 % of the U.S. population are female and 15% are older than age 65, can we conclude that (.52)(.15) = 7.8% are women older than age 65? A Yes, by the multiplication rule. B Yes, by conditional probabilities. C Yes, by the Law of Large Numbers. D No, because the events are not independent. E No, because the events are not mutually exclusive.
e
Given x=3.8, sx=1.2, y=2.7, sy=.5 and r = .64. Find the equation of the LSRL. a. y=2.7+3.8 x b. y=2.7+1.536 x c. y=1.687+1.563 x d. y=2.7+.267 x e. y=1.687+.267 x
e
In an experiment the primary purpose of blocking is to reduce ... a. bias. b. confounding. c. randomness. d. undercoverage. e. variation.
e
Meg has a set of data with a correlation of r = .83. Elise has a data set with a correlation r = -.83. What can you conclude about the two sets of data? a. Both data sets display a strong linear association. b. In Meg's data, 83% of the data points are closely associated c. In Elise's data, 83% of the variability in y can be explained by the linear association with x. d. Meg's data is more linear than Elise's data. e. Nothing can be concluded about the two sets of data.
e
Populations P1 and P2 are normally distributed and have identical means. However, the standard deviation of P1 is twice the standard deviation of P2. What can be said about the percentage of observations falling within two standard deviations of the mean for each population? A The percentage of P1 is twice the percentage of P2. B The percentage of P1 is greater, but not twice as great, as the percentage of P2. C The percentage for P2 is twice the percentage for P1. D The percentage of P2 is greater, but not twice as great, as the percentage of P1. E The percentages are identical.
e
Suppose X and Y are random variables with E(X) = 25, VAR(X) = 3, E(Y) = 30, and VAR(Y) = 4. What are the expected value and variance of the random variable X + Y? A E(X+Y) = 55, VAR(X+Y) = 3 B E(X+Y) = 55, VAR(X+Y) = 5 C E(X+Y) = 55, VAR(X+Y) = 7 D E(X+Y) = 27.5, VAR(X+Y) = 7 E There is insufficient information to answer this question.
e
Suppose you toss a fair coin ten times and it comes up heads every time. Which of the following is a true statement? A By the Law of Large Numbers, the next coin toss is more likely to be a tails than another heads. B By the properties of conditional probability, the next toss is more likely to be heads given that the last ten tosses in a row have been heads. C Coins actually do have memories, and thus what comes up on the next toss is influenced by the past tosses D The Law of Large Numbers tells how many tosses will be necessary before the percentage of heads and tails are again in balance. E The probability that the next toss will again be heads is .5.
e
The January 2005 Gallup Youth Survey telephoned a random sample of 1,028 U.S. teens and asked these teens to name their favorite movie from 2004. Napoleon Dynamite had the highest percentage with 8% of teens ranking it as their favorite movie. Which is true? I. The population of interest is all U.S. teens. II. 8%is a statistic and not the actual percentage of all U.S. teens who would rank this movie as their favorite. III. This sampling design should provide a reasonably accurate estimate of the actual percentage of all U.S. teens who would rank this movie as their favorite. a. I only b. II only c. III only d. I and III e. I, II, and III
e
The Women's Health Study randomly assigned nearly 40,000 women over the age of 45 to receive either aspirin or a placebo for over 10 years to examine the effect of aspirin on cancer risk to healthy women. This long-term trial was best conducted as a. a census b. an observational study c. a randomized comparative experiment d. a single-blind randomized comparative experiment e. a double-blind randomized comparative experiment
e
The average noise level at a restaurant is 30 decibels with a standard deviation of 4 decibels. Ninety-nine percent of the time it is below what value? A 20.7 B 32.0 C 33.4 D 37.8 E 39.3
e
The key difference between an observational study and an experiment is a. the number of variables that are being studied b. the use of randomized selection for participation c. the ability to replicate the study d. the creation of groups of homogenous subjects to study e. the application of a treatment to manipulate a variable
e
What is the probability that a randomly selected student has a GPA under 2.0 given that he has skipped many classes? A. .080 B .281 C .285 D .314 E .727
e
What is the probability that a student from this class eats breakfast or flosses their teeth? (A) 9% (B) 11% (C) 34% (D) 57% (E) 91%
e
What is the sensitivity of the test? That is, what is the probability of testing positive given that the person has HIV? A .070 B .130 C .538 D .583 E .875
e
What is the specificity of the test? That is, what is the probability of testing negative given that the person has does not have HIV? A .125 B .583 C .870 D .950 E .946
e
Which is important in designing a good experiment? I. Randomization in assigning subjects to treatments. II. Control of potentially confounding variables. III. Replication of the experiment on a sufficient number of subjects. a. I only b. I and II c. I and III d. II and III e. I, II and III
e
Which of the following are true statements? I In well-designed observational studies, responses are systematically influenced during the data collection. II In well-designed experiments, the treatments result in responses that are as similar as possible. III A well-designed experiment always has a single treatment but may test that treatment at different levels. a I only b II only c III only d II and II e None of these statements is true.
e
Which of the following are true statements? I The area under a standard normal curve between 0 and 2 is twice the area between 0 and 1. II The area under a standard normal curve between 0 and 2 is half the area between 0-2 and 2. III For the standard normal curve, the interquartile range is approximately 3. A I and II B I and III C II and III D I, II, and III E None of the above gives the complete set of true responses.
e
Which of the following are true statements? I. Convenience samples are rarely beneficial II. Blocking should be used if race, gender, or some other factor may affect our results III. All experiments should be double blind if possible a. I only b. II only c. I and II d. I and III e. I, II, and III
e
Which of the following is not a necessary component of a well-designed experiment? a. Imposing a treatment b. Randomization c. Replication d. Control of confounding variables e. Stratification
e
Which of those variables about German Shepherds is most likely to be described by a Normal model?
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