S1 AP Stats Final
You are assuming that there are at least 750 female students at your high school.
A 2011 poll by the Pew Research Center found that 66% of young women ages 18 to 34 rated a high-paying career high on their list of life priorities. Let's assume for this problem that 66% of the female students in your high school consider a high-paying career as a priority. You plan to take a sample of 75 female students. If you calculate the variance of the sampling distribution of proportions for a sample of 75 using √(0.66)(0.34)/75 , what assumption are you making about this situation?
Two factors and 6 treatments
A biologist is studying the effect of different nutrients and different levels of salinity (salt) in water on the growth of a certain species of fish. Ten fish are to be assigned at random to each of 12 similar tanks in a controlled environment. The biologist wants to use combinations of 2 different nutrients and 3 different salinity levels as treatments. In this experimental design, how many factors and treatments are there?
0.6597
A blood test for a certain disease has a false positive rate of 0.01 and a false negative rate of 0.05. (Recall that "false positive" means the test returns a positive result when the subject does not have the disease). Suppose that 2% of a certain population has the disease. If a random individual from this population tests positive, what is the probability that this person actually has the disease?
The number 26% is a statistic.
A news website claims that 30% of all Major League Baseball players use performance-enhancing drugs ("PEDs") Indignant at this claim, league officials conducts a survey in which 200 randomly selected baseball players are tested. Of the tested players, 52, or 26%, test positive. Which of the following statements about this situation is true?
mue= $2500 SD= $200
A widget manufacturer estimates that the total weekly cost in dollars, C, to produce x widgets is given by the linear function C(x) = 500 + 10x, where the intercept 500 represents the fixed cost of manufacturing any number of widgets and the slope 10 represents the variable cost of producing x widgets. Analysis of weekly widget production reveals that the number of widgets X produced in a week is a random variable with mean and standard deviation =20 What are the mean and the standard deviation of C?
0.9885
At a high school with 800 students, 80% of the students ride the school bus. If 20 students are selected randomly (without replacement) and we let X = the number of students in the sample who ride the bus, what is the probability that at least one of the students doesn't ride the bus?
One
According to the 1.5 × IQR rule, how many outliers are there in the data set 72, 110, 114, 115, 118, 123, 144, 156?
a randomized block design with six blocks and three treatments
An agricultural scientist wants to compare the effect on yield of three different methods of growing blueberries. To control for variables such as soil condition and location, he plants 30 plots on each of six different farms. On each farm, 10 of the 30 plots are assigned to each of the three treatments (growing methods). She measures and compares the marketable yield of blueberries produced by each plot. Which of the following best describes the design of this experiment?
The Brand A bulb has a longer life relative to its brand.
An office uses two brands of fluorescent light bulbs in its overhead light fixtures. From past experience, it is known that Brand A bulbs have a mean life length of 3000 hours and a standard deviation of 200 hours, while Brand B bulbs have a mean life length of 2700 hours and a standard deviation of 250 hours. Which bulb has a longer life relative to all bulbs of its brand, a Brand A bulb that lasts 3150 hours or a Brand B bulb that lasts 2850 hours?
Because the sample is less than 10% of the population, it is appropriate to use the binomial distribution even though the samples are not strictly independent.
At a high school with 800 students, 80% of the students ride the school bus. If 20 students are selected randomly (without replacement) and we let X = the number of students in the sample who ride the bus, then X does not exactly have a binomial distribution. Why is it nevertheless appropriate to approximate probabilities for X using the binomial distribution for n = 20 and p = 0.8?
II and V only
Consider the following five sets of outcomes from random phenomena: I. The total number of points scored in a randomly selected college football game. II. Lifespan in hours of a randomly selected halogen light bulb. III. The number of passengers in a randomly selected city bus. IV. The airline of the next plane to land at O'Hare International Airport. V. Length in inches of the next rattlesnake caught in a trap. Which of the above are continuous random variables?
12.1%
Suppose we classify 315 randomly selected college students according to their general major field and their self-described political viewpoint. The table presents the results. Sciences Business Humanities Social Sciences Liberal 17 12 32 30 Moderate 33 40 23 20 Conservative 35 38 17 18 What percentage of all students surveyed are conservatives majoring in business?
35.2%
Suppose we classify 315 randomly selected college students according to their general major field and their self-described political viewpoint. The table presents the results. Sciences Business Humanities Social Sciences Liberal 17 12 32 30 Moderate 33 40 23 20 Conservative 35 38 17 18 What percentage of liberals surveyed were humanities majors?
91, 116, 108
Suppose we classify 315 randomly selected college students according to their general major field and their self-described political viewpoint. The table presents the results. Sciences Business Humanities Social Sciences Liberal 17 12 32 30 Moderate 33 40 23 20 Conservative 35 38 17 18 Which of the following list of numbers is a marginal distribution of the variable political viewpoint?
A higher proportion of students with a liberal political viewpoint major in the humanities, and a higher proportion of moderates and conservatives major in business.
Suppose we classify 315 randomly selected college students according to their general major field and their self-described political viewpoint. The table presents the results. Sciences Business Humanities Social Sciences Liberal 17 12 32 30 Moderate 33 40 23 20 Conservative 35 38 17 18 Which of the following characteristics of these data supports the conclusion that there is an association between political viewpoint and general major field?
A and B are independent.
Suppose we toss a fair penny and a fair nickel. Let A be the event that the penny lands heads and B be the event that the nickel lands tails. Which one of the following is true about events A and B?
The distribution of means of all possible samples of size 50 that could be selected from the students in your school.
Suppose you take a sample of 50 students from your school and find the mean height of the students in your sample. Which one of the following does the sampling distribution of the mean describe?
The mean of the sample data.
Suppose you take a sample of 50 students from your school and measure their height. Which one of the following is a random variable?
Approximately Normal
The American Community Survey estimates that the mean household income in the United States in 2011 was $69,800, with a standard deviation of $17,000. The distribution is strongly skewed to the right. Suppose we take a simple random sample of 36 households. Which of the following accurately describes the shape of the sampling distribution of the mean household income?
$72,180
The American Community Survey estimates that the mean household income in the United States in 2011 was $69,800, with a standard deviation of $17,000. The distribution is strongly skewed to the right. Suppose we take a simple random sample of 36 households. Which of the following is closest to the 80th percentile for the sample mean?
0.0455
The American Community Survey estimates that the mean household income in the United States in 2011 was $69,800, with a standard deviation of $17,000. The distribution is strongly skewed to the right. Suppose we take a simple random sample of 36 households. Which of the following is closest to the probability that the sample mean is less than $65,000?
There is a moderately weak, positive linear relationship between height and foot length.
The following scatterplot describe the relationship between height (in cm) and foot length (also in cm) for 12 randomly selected students from the British Census @ Schools database. Which of the following is the best description of this relationship?
Skewed to the left
The graph below is a Normal probability plot of test scores for students in Mr. Olivier's precalculus classes. Based on this plot, which of the following is the best description of the shape of the distribution of test scores?
Mean > Median
The histogram below shows the typical travel time to school (self-reported) for 50 high school students. Which of the following statements is true about the mean and median of this distribution?
0.1018
There are 20 multiple-choice questions on an exam, each having four possible responses, of which only one is correct. Each question is worth 5 points if answered correctly. Suppose that a student guesses the answer to each question, with her guesses from question to question being independent. If the student needs at least 40 points to pass the exam, the probability that she passes is closest to
9.68
There are 20 multiple-choice questions on an exam, each having four possible responses, of which only one is correct. Each question is worth 5 points if answered correctly. Suppose that a student guesses the answer to each question, with her guesses from question to question being independent. The standard deviation of the student's score on the exam is
25
There are 20 multiple-choice questions on an exam, each having four possible responses, of which only one is correct. Each question is worth 5 points if answered correctly. Suppose that a student guesses the answer to each question, with her guesses from question to question being independent. The student's expected (mean) score on this exam is
(0.7)^3 (0.3)
In a certain large population, 70% are right-handed. You need a left-handed pitcher for your softball team and decide to find one by asking people chosen from the population at random. (We assume that once you do find a left-hander, he or she will be happy to join your team and will say yes.) Which of the following expression gives the probability that the first left-hander you finder is the fourth person you ask?
0.343
In a certain large population, 70% are right-handed. You need a left-handed pitcher for your softball team and decide to find one by asking people chosen from the population at random. (We assume that once you do find a left-hander, he or she will be happy to join your team and will say yes.) Which of the following is closest to the probability that you will have to ask four or more people before finding your first left-hander?
0.449
In a large city, 82% of residents own a cell phone. Suppose that we randomly select three city residents. What is the probability that at least one of the three residents does not own a cell phone? [The city is large enough so that we can assume independence].
$0.40
In a particular game, a single card is randomly chosen from a box that contains 3 red cards, 1 green card, and 6 blue card. If a red card is selected, you win $2. If a green card is selected, you win $4. If a blue card is selected, you lose $1. Let X be the amount that you win. The expected value of X is
The sampling variability is about the same in both cases.
In a simple random sample of 1000 Americans, it was found that 61% were satisfied with the service provided by the dealer from which they bought their car. In a simple random sample of 1000 Canadians, 58% said that they were satisfied with the service provided by their car dealer. Which of the following statements concerning the sampling variability of these statistics is true?
The slope would increase.
Ms. Kreppel is interested in the relationship between her students' final exam scores and their scores on a pre-test they took at the beginning of the year. Below is a scatterplot showing this relationship for the 18 students in her class. How would the slope of the least-squares regression line change if the individual whose point is circled were removed from the data set?
13.8.
Scores on the American College Testing (ACT) college entrance exam follow a Normal distribution with mean 18 and standard deviation 6. Lisa's standardized score on the ACT was z = -0.7. What was her actual ACT score?
17.6%
Below is a dotplot of voter turnout (as a percentage of voting-age population) for the 50 states—plus the District of Columbia—in a recent presidential election. Approximately what percentage of the states had a turnout above 65%?
8
Below is a dotplot of voter turnout (as a percentage of voting-age population) for the 50 states—plus the District of Columbia—in a recent presidential election. What is the interquartile range?
Skewed slightly left, centered at about 62%, with a range of 24 percentage points.
Below is a dotplot of voter turnout (as a percentage of voting-age population) for the 50 states—plus the District of Columbia—in a recent presidential election. Which of the following best describes this distribution?
Using proportionally-sized trees exaggerates differences between countries.
Below is a graphical presentation of information from the World Bank about the percentage of land in four East African countries that is forest. What's wrong with this method of presenting information?
Too high
Below is a residual plot for the regression of the number of employees of Microsoft Inc. on year for the years from 1976 to 1989. (Note that this is a residual plot, not a scatterplot!) There is no observed value for the year 1983. If we were to use this regression to predicted the number of employees in 1983, which of the following is most likely to describe the accuracy of our prediction?
To reduce bias, you should make an effort to contact and survey the 1153 teachers who did not respond to the first mailing.
You want to know the opinions of American high-school teachers on the issue of establishing a national proficiency test as a prerequisite for graduation from high school. You obtain a list of all high-school teachers belonging to the National Education Association (the country's largest teachers' union) and mail a survey to a random sample of 2500 teachers. In all, 1347 of the teachers return the survey. Which of the following statements about this situation is true?
S = { -2, 1, 4, 7}
A game consists of drawing three cards at random from a deck of 52 playing cards. You win 3 points for each red card that is drawn. It costs 2 points each time you play. For one play of this game, the sample space S for the net number of points you gain (after deducting the cost of play) is
Only students with particularly strong opinions—and most likely, negative opinions—are likely to take the trouble to evaluate teachers on the site.
A high-school principal discovers a web site that invites students to "Rate Your Teacher" one a 5-point scale in several categories. He thinks this might help him decide who his best teacher are, but the school's statistics teacher tells him to ignore any information from the site. Why?
0.5
A jar contains 10 red marbles and 15 blue marbles. If you randomly draw two marbles from the jar (without replacement), what is the probability that they are the same color?
undercoverage
A poll of American adults' opinions about efforts to reform Social Security was conducted in 2004-2005 by the AARP, the nation's largest organization for retired people. The poll results were criticized in some quarters because they included no respondents under the age of 30, even though voters aged 18 to 29 made up 17% of the 2004 electorate. By contrast, respondents aged 60 and above made up 34% of the sample but were only 24% of the electorate. This poll is most likely subject to which of the following types of bias?
an observational study.
A researcher in early childhood education believes that kindergarten-age children are more receptive to help from a female teacher than from a male teacher. From a list of kindergarten teachers in the state, the researcher randomly samples four classes with male teachers and four classes with female teachers. The students in the classes are interviewed, and a measure of how receptive the students in each class are to help from the teacher is determined. This study is an example of
a convenience sample.
A researcher is interested in the cholesterol levels of adults in the city she lives in. A cholesterol-screening program is set up in the downtown area during the lunch hour. Individuals can walk in and have their cholesterol measured for no charge. In one lunch hour, 173 people use the service, and their average cholesterol level is 217.8. The sample obtained here is an example of
Predictions using the regression line will be more reliable for large x than for small x.
A residual plot displays a "reverse fan" arrangement, with the spread of points about the line (residual = 0) gradually decreasing from left to right (that is, as x increases). Which statement would be a correct interpretation of this plot?
There are 300 + 600 = 900 Democrats, 500 + 300 = 800 Republicans, and 200 + 100 = 300 Other in the set of all voters.
A review of voter registration records in a small town yielded the following table of the number of males and females registered as Democrat, Republican, or some other party affiliation. Male Female Democrat 300 600 Republican 500 300 Other affiliation 200 100 Which of the following bar graphs represents the distribution of party affiliation among all voters in this town?
neither (A) nor (B)
A set of 10 playing cards consists of 5 red cards and 5 black cards. The cards are shuffled thoroughly, and we draw 4 cards one at a time and without replacement. Let X = the number of red cards drawn. The random variable X has which of the following probability distributions?
Early childhood nutrition is an explanatory variable.
A sociologist is studying the relationship between early childhood nutrition and academic achievement in middle school among children in a certain city. Which of the following statements about the variable "early childhood nutrition" is correct?
Children in this city who have a healthy diet in early childhood tend to do better in middle school.
A sociologist studying the relationship between early childhood nutrition and academic achievement in middle school among children in a certain city finds that the correlation between these two variables is 0.86. Which of the following conclusions can he draw from this study?
The 25 men who received and returned the questionnaire.
A sociologist wants to study the attitudes of American male college students toward marriage. She gives a questionnaire to 25 of the men enrolled in Sociology 101 at her college. All 25 men complete and return the questionnaire. Which of the following is the sample in this situation?
an experiment, but not a double-blind experiment.
A study involving women aged 50 to 75 randomly assigned equal numbers of women to an exercise program (at least 45 minutes of moderate walking or riding an exercise bike five times a week) and to a stretching program (15 to 30 minutes of stretching three times a week, under the supervision of an exercise physiologist). It was found that a higher percentage of women in the exercise group reported improved sleep than did women in the stretching group. This study is an example of
r = 0.9
A study showed that students who spend more time studying for statistics tests tend to achieve better scores on their tests. In fact, the number of hours studied turned out to explain 81% of the observed variation in test scores among the students who participated in the study. What is the value of the correlation between the number of hours studied and test score?
(.65 (.15) .10) .10
A survey of high school students finds that 80% of them get news on current events from the internet, 25% of them get news from television, and 15% use both sources. Which of the following is an accurate Venn diagram of this information? [Let "I" = Get news from internet and "T" = Get news from Television.]
X and Y are independent.
If X and Y are random variables, and which of the following is a condition for calculating by using ?
The proportion of outcomes greater than 1.5 is equal to 0.25.
For the density curve shown, which of the following statements is true?
Mean 140 grams, standard deviation 22.4 grams.
Fuji apples grown at a certain orchard have a mean weight of 5.2 ounces with a standard deviation of 0.8 ounces. Suppose the scale the orchard owner uses systematically underweighs apples by 0.2 ounces and also weighs the apples in grams, rather than ounces. What would the mean and standard deviation of these apples' weights be as determined by this scale? (Note: 1 ounce ≈ 28 grams).
0.125
In the wild, 400 randomly selected blooming azalea plants are observed and classified according to flower petal color (white, pink, or orange) and whether or not they have a fragrance. The table gives the results. White Pink Orange Totals Fragrance 22 104 140 266 No Fragrance 98 16 20 134 Totals 120 120 160 400 If a single azalea plant is selected at random and found to be orange, what is the probability that it has no fragrance?
0.595
In the wild, 400 randomly selected blooming azalea plants are observed and classified according to flower petal color (white, pink, or orange) and whether or not they have a fragrance. The table gives the results. White Pink Orange Totals Fragrance 22 104 140 266 No Fragrance 98 16 20 134 Totals 120 120 160 400 If a single azalea plant is selected at random, which one of the following is the probability that it has pink flower petals or no fragrance?
140/120, /=/ 266/400
In the wild, 400 randomly selected blooming azalea plants are observed and classified according to flower petal color (white, pink, or orange) and whether or not they have a fragrance. The table gives the results. White Pink Orange Totals Fragrance 22 104 140 266 No Fragrance 98 16 20 134 Totals 120 120 160 400 Suppose a single azalea plant is chosen at random. Which of the following expressions establishes that the events "Fragrance" and "Pink" are independent?
You want to display the distribution of favorite color for the students in your statistics class.
In which of the following situations would a pie chart be an appropriate graph to use to summarize your data?
The third quartile of the Group 1 distribution is larger than the maximum value of the Group 2 distribution (that is, 25% of the Group 1 values are larger than any Group 2 value).
Independently selected groups of middle-school children were given a poem to memorize. After a certain period of time, they were asked to recall as much of the poem as they could. A back-to-back stemplot of the distribution of the number of words that each group of children could correctly remember is displayed below. Which of the following statements about these data is true?
5
Javier's school bus is always late. Below are data on how many minutes late the bus was for 15 days in February. 1 2 2 2 3 3 4 4 4 5 6 7 8 10 12 What is the 60th percentile of this distribution?
The mean and standard deviation.
Jerome's summer reading list has 8 books, and he is examining the number of pages in each book. After calculating the mean, median, standard deviation, and interquartile range, he realized that the longest book is actually 100 pages longer than he thought it was. Which of his measurements does he need to recalculate?
0.5
Let X = the number of times that a randomly selected customer visits a grocery store during a one-week period. Suppose that the probability distribution of X is as follows: X 0 1 2 3 P(X)0.1 0.4 0.4 0.1 Determine the probability that a randomly chosen customer visits the grocery store at least twice during a one-week period.
On average, the number of students who are late to Mr. Rooney's class on a randomly selected day is 2.
Let Z = the number students in Mr. Rooney's English class who arrive late on a randomly selected day. The expected value of Z is 2. Which one of the following is the best interpretation of what this means?
Sebastien's study is subject to confounding.
Many people believe that taking zinc lozenges reduces the severity and duration of the common cold. Sebastien decides to conduct a study at his school to explore this claim. He sends a survey to a simple random sample of 100 students, asking them to if they took zinc lozenges or not during their last cold, and how long they experienced cold symptoms. He found that students who took zinc had a mean cold duration that was 1.2 days lower than those who did not take zinc. Which of the following statements about his study is true?
2.2
Ms. Kreppel is interested in the relationship between her students' final exam scores and their scores on a pre-test they took at the beginning of the year. A scatterplot of the data for the 18 students in her class shows linear relationship for these variables. The equation of the least-squares regression line is Final Exam= 34.2 + 0.60 (Pre-Test) One student scored a 76 on the pre-test and an 82 on the final exam. Which of the following is that student's residual?
For each one-unit increase in pre-test score, the model predicts, on average, a 0.60 unit increase in exam score.
Ms. Kreppel is interested in the relationship between her students' final exam scores and their scores on a pre-test they took at the beginning of the year. A scatterplot of the data for the 18 students in her class shows linear relationship for these variables. The equation of the least-squares regression line isFinal Exam = 34.2 + 0.60 (Pre-test)Which of the following is a correct interpretation of the slope of this regression model?
The correlation between amount of fertilizer and yield of tomatoes was found to be r = 0.33.
One of the following is a correct statement involving correlation. The other two contain blunders. Which one is correct?
0.35
Research on eating habits of families in a large city produced the following probabilities if a randomly selected household was asked "How often during the week do you have a vegetarian (meatless) main dish at dinnertime?" Outcome Probability Three or more times a week 0.06 Twice a week 0.10 Once a week 0.49 Never ? What is the probability that a randomly selected household never has a vegetarian main dish at dinnertime?
an experiment
Researchers in Britain randomly divided a large number of premature babies into three groups. One received donated breast milk, one received infant formula made for premature babies, and the third received regular infant formula. Each diet was used for one month as a sole food or as a supplement to mother's milk. Sixteen years later, the children returned and had their blood pressure measured. It was found that diastolic and systolic blood pressure both tended to be lower in the children who were fed breast milk than in the children who were fed formula. This study is an example of
140 grams.
The cumulative relative frequency graph below describe the distribution of weights (in grams) of tomatoes grown in a laboratory experiment. Which of the following weights is closest to the median of the distribution?
0.0778
The daily total sales (excluding Saturday) at a small restaurant has a probability distribution that is approximately Normal with a mean of and a standard deviation of = $120 The probability the sales will exceed $700 on a given day is approximately
The first quartile for the two sections is the same.
The following box plots show the distribution of test scores in Ms. Williams's two sections of calculus. Based on these box plots, which one of the following statements must be true?
Height = 117.99 + 1.878(Foot length)
The following computer output describes the relationship between y = height (in cm) and x = foot length (also in cm) for 12 randomly selected students from the British Census @ Schools database. The scatterplot for this relationship show a roughly linear shape. Which of the following is an equation of least-squares regression line for these data?
If we use the regression equation to predict height from foot length, our predictions will be, on average, off by 7.39858 centimeters.
The following computer output describes the relationship between y = height (in cm) and x = foot length (also in cm) for 12 randomly selected students from the British Census @ Schools database. The scatterplot for this relationship show a roughly linear shape. Which of the following is the correct interpretation of the number s = 7.39858?
Approximately Normal, with mean 0 and standard deviation 1.
The lifetime of 9-volt battery in constant use has an approximately Normal distribution with a mean of 516 hours and a standard deviation of 20 hours. Which of the following best describes the distribution of standard scores for the lifetimes of such batteries?
0.4207
The lifetime of a 2-volt battery in constant use has a Normal distribution with a mean of 516 hours and a standard deviation of 20 hours. The proportion of batteries with lifetimes that exceed 520 hours is approximately
541.6 hours
The lifetime of a 9-volt battery in constant use has an approximately Normal distribution with a mean of 516 hours and a standard deviation of 20 hours. Which of the following is the approximate lifetime of a battery that lasts longer than 90% of all batteries?
62
The owner of a convenience store keeps track of how many customer buy lunch food during the "noon rush" each day for four days and calculates that the mean number of customers for those four days is 52. How many customers must come in on the fifth day to make the five-day mean 54?
There is a negative correlation r between weight and time for both males and females.
The points in the scatterplot represent paired observations (x, y) where x is an individual's weight and y is the time (in seconds) it takes for walking on a treadmill to raise the individual's pulse rate to 140 beats per minute. The open circles correspond to females and the dark squares to males. From the scatterplot, which conclusion we can make?
If a very large number of people are selected, the proportion of left-handed people will be very close to.
The probability of a randomly selected person being left-handed is . Which one of the following best describes what this means?
The mean is larger than the median.
The stem-and-leaf diagram below gives the distribution of the ages in years of 20 participants at a family reunion. 0 7888 1 23689 2 45799 3 9 4 5 8 6 5 7 89 8 9 1 Which of the following statements about the distribution is correct?
0.2
The time in minutes X that you must wait before a train arrives at your local subway station is a uniformly distributed random variable that takes on values between 5 minutes and 15 minutes. That is, the density curve of the distribution of X has constant height between X = 5 and X = 15 and height 0 outside this interval. Determine P(6 < x < 8).
0.0784
The weight of a medium-sized orange selected at random from a large bin of oranges at a local supermarket is a Normally distributed random variable with mean μ = 12 ounces and standard deviation σ = 1.2 ounces. Suppose we independently select two oranges at random from the bin. What is the probability that the difference in the weights of the two oranges exceeds 3 ounces?
1.70 ounces.
The weight of a medium-sized orange selected at random from a large bin of oranges at a local supermarket is a random variable with mean μ = 12 ounces and standard deviation σ = 1.2 ounces. Suppose we independently select two oranges at random from the bin. The difference in the weights of the two oranges (the weight of the first orange minus the weight of the second orange) is a random variable with a standard deviation equal to
between 68% and 95%.
The weights of cockroaches living in a university dormitory follow a Normal distribution with mean 80 grams and standard deviation 5 grams. The percentage of cockroaches having weights between 72 grams and 88 grams must be
We cannot determine whether social media influences satisfaction, nor can we generalize our findings to the entire school.
To examine how people respond emotionally to social media. A social scientist asks for volunteers at a local high school to fill out a survey. The survey asks how much time the subjects spent on Facebook, Twitter, and Tumblr in the last 48 hours, and then asks a series of questions that assess the subjects level of satisfaction with their lives at the present time. The scientist divides the subject up into "high social media use" and "low social media" use and then compares the satisfaction ratings of the two groups. Which of the following statements is true about this study?
-0.67
What is the 25th percentile of the standard Normal distribution?
Using many subjects to reduce the impact of variation arising from random assignment.
Which of the following best describes the purpose of replication in an experimental design?
Write the names of the 1000 people on slips of paper. Put the slips of paper in a (large!) hat and draw out 50 slips.
Which of the following is a legitimate method for taking a simple random sample of size 50 from a population of 1000 people?
X -1 0 1 P(X)0.3 0.4 0.3
Which of the following probability distributions of a discrete random variable X is a legitimate probability distribution?
The sum of the squared differences between observed values of the response variable and values of the response variable predicted by the model.
Which of the following quantities is minimized by the least-squares regression line?
It has the same sign as the correlation coefficient r.
Which of the following statements about the slope of the least-squares regression line is true?
Assign the numbers 0 through 4 to "heads" and 5 through 9 to "tails." Read 10 one-digit numbers from a random digits table, and count this simulation as a "success" if there is at least one run of 3 or more heads. Repeat this 500 times and divide the total number of "successes" by 500.
You want to perform a simulation to estimate the probability of getting at least one run of 3 heads in a row in 10 flips of a fair coin. Which of the following describes a correct simulation for estimating this probability?
stratified sampling
You would like to compare the level of mathematical knowledge among 15-year-olds in the United States and Japan. To do this, you plan to give a mathematics achievement test to random samples of 1000 15-year-olds in each of the two countries. To ensure that the samples will include individuals from all different socioeconomic groups and educational backgrounds, you will randomly select 200 students from low-income families, 400 students from middle-income families, and 400 students from high-income families in each country. The sampling procedure being used here is
