Statistics Ch 6, 10, 11, 15
At a small college, all entering freshman must take a foreign language class, chosen from the languages. The probability for the language studied by a randomly selected freshman is summarized in the following table Spanish: ? French: 0.12 Swahili: 0.09 Chinese: 0.19 Arabic: 0.12 The probability that the freshman is studying Chinese or Swahili is?
0.28
An outlier is_____
A point in a scatterplot that does not follow the same pattern as the other points
A study attempts to compare two sunscreens. Each of 50 subjects with varying skin complexions will use both sunscreens - Screen A on one side of his of her body and Screen B on the other side. For each subject, a coin is tossed in order to determine which side receives Screen A and which receives Screen B. Researchers measure the amount of ultraviolet light exposure over both treated areas for each subject. This is an example A. A matched pairs experiment B. A double-blind observational study C. A stratified analysis D. The placebo effect
A. A matched pairs experiment
You can describe the overall pattern of a scatterplot by the A. Form, direction, and strength B. Normal distribution C. Number of points D. None of the above
A. Form, direction, and strength
If the correlation coefficient (r) = 1.00, then
All of the data points must fall exactly on a straight line with a positive slope
In a survey of sleeping habits, 8400 national adults were selected randomly A. 8400 is the size of population studied B. 1.8 is a statistic and represents an estimate of the unknown C. 1.8 is a parameter D. none of the above
B
Assuming a linear relationship between X and Y, if the coefficient of correlation (r) equals -30, A. There is no correlation B. The slope (b1) is negative C. Variable X is larger than variable Y D. The variance of X is negative
B. The slope (b1) is negative
According to the Current Population Survey, the following table summarizes probabilities for randomly selecting a full-time student in various age groups: Age 15-17 - .007 18-24 - .573 25-34 - .260 35 or older - .160 If we randomly select a full-time student, the probability that he/she is 20-34 years old is A. 0.50. B. 0.703. C. 0.833. D. Impossible to determine from the information provided.
D. Impossible to determine from the information provided.
To say that a six-sided die is "fair" means that when it is rolled, each of the outcomes 1, 2, 3, 4, 5, and 6 has probability 1/6 of ending face up. This means A. In the next 6 rolls of the die, exactly one of the outcomes will be 1 B. In the next 6 rolls of the die, at least one of the outcomes will 1 C. In the next 6 rolls of the die, at most one of the outcomes will be 1 D. None of the above
D. None of the above
What do we know about the correlation between change in blood pressure and type of music? A. It is negative B. It is positive C. It is first negative then positive D. None of the above
D. None of the above
Which of the following statements is true? A. When calculating the correlation, r, it is important to make sure y is the explanatory variable and the x is the response variable B. When calculating the correlation, r, it is important to make sure x is the explanatory variable and the y is the response variable C. The correlation, r, can be any number between -100 and 100 D. None of the above
D. None of the above
Response variables are also called ____ variables
Dependent
When examining a scatterplot for direction, you are looking to see if ___ A. High values of the two variables in the scatterplot tend to occur together B. High values of one variable tend to occur with low values of the other variable C. There is a positive association D. There is a negative association E. All of the above F. A and C G. B and D
E. All of the above
Percent tested positive for malaria is the ___ variable A. Independent B. Dependent C. Response D. Explanatory E. B and C F. A and B
E. B and C
Correlation is resistant against outliers
False
There is a strong linear relationship between percentage of people tested positive for malaria and precipitation T/F
False
Time plots are special scatterplots where the response variable, y, is a measure of time. T/F
False
Positive linear relationships are represented by values of the correlation, r, that are___
Greater than zero
When creating a scatterplot, which axis should be used for the explanatory variable?
Horizontal
Negative linear relationships are represented by values of the correlation, r, that are_____
Less than zero
A researcher studies the relationships between the Math SAT score plus verbal SAT score and the grade point average (GPA) of college students at the end of their freshman year.
None of the above
A scatterplot is a graphical tool for displaying the relationship between two ___ variables measured on the same individuals
Quantitative
The law of large number states that as the number of observations drawn at random form a population with finite mean mu increase, the mean x bar of the observed values
Tends to get closer and closer to the population mean mu
The sampling distribution of a statistic is
The distribution of values taken by a statistic in all possible samples of the same size from the same population
A statistic is said to be unbiased if
The mean of its sampling distribution is equal to the true value of the parameter being estimated
Correlation is a measure of the direction and strength of the linear (straight-line) association between two quantitative variables. The analysis of data from a study found that the scatterplot between two variables, x and y, appeared to show a straight-line relationship and the correlation was calculated to be -0.84. this tells us
There is a strong linear relationship between x and y with smaller x. Values tending to be associated with larger values of the y variable
Time plots are special scatterplots where the explanatory variable, x, is a measure of time T/F
True
For a certain data set the correlation coefficient between X and Y was found to be -0.002. Interpret the meaning of the correlation coefficient
X and Y are uncorrelated
Suppose a large population has mean mu and standard deviation, and a simple random sample of size (n) is taken. The sampling distribution of the sample mean x bar has mean and variance respectively equal to
mean mu and standard dev./size (n)
In a skills competition involving many different events, two particular contestants were tied on each and every event, always getting the identical score. For the competition, the correlation between the scores of these two contestants is:
1
Suppose that two very large companies (A and B) each select random samples of their employees. Company A had 5000 employees. Company B has 15,000 employees. In both surveys, the company will record the number of sick days taken by each sampled employee. If each company randomly selects 50 employees for the survey, which of the following is true about the sampling distributions of the sample means (the mean number of sick days) A. The sampling distributions of the sample means will have about the same standard deviation. The standard deviation for sampling distribution of a sample mean depends only on the sample size, not the population (company size) B. Since company A is surveying a higher percent of its employees, the standard deviation of the sampling distribution for its sample mean will be smaller than that for Company B (the larger company). Larger companies should take larger samples C. Since company B is a larger company, the SD for its sampling distribution of the sample mean is smaller. The larger a population, the smaller the SD of a sample mean's sampling distribution. D. None of the above
A.
Two variables are positively associated when ___ A. Above average values of one tend to accompany above average values of the other and vice versa B. Above average values of one tend to accompany below average values of the other, and vice versa C. Both variables have an outlier D.None of the above
A. Above average of one tend to accompany above average values of the other and vice versa
A local health club, a researcher samples 75 people whose primary exercise is cardiovascular and 75 people whose primary exercise is strength training. The researcher's objective is to assess the effect of type of exercise on cholesterol. Each subject reported to a clinic to have his or her cholesterol measured. The subjects were unaware of the purpose of the study, and the technician measuring the cholesterol was not aware of the subject's type of exercise. This A. An observational B. An experiment, but not a double-blind experiment C. A double-blind experiment D. A matched pairs experiment
A. An observational study
To investigate whether women are more likely than men to prefer Democratic candidates, a political scientist selects a large sample of registered voters, both men and women. She asks every voter whether they voted for the Republican or the Democratic candidate in the last election. This is: A. An observational study B. A multistage sample C. A double-blind experiment D. A block design
A. An observational study
A news release for diet products company reports: "There's good news for 65 million Americans currently on a diet." Its own study showed that people who lose weight can keep it off. The sample was 20 graduates of the company's program who endorsed the program in commericals. The results of the sample are probably A. Biased, overstating the effectiveness of the diet. B. Biased, understanding the effectiveness of the diet C. Unbiased since the people in the sample are nationally recognized individuals D. Unbiased, but they could be more accurate. A larger sample size should be used.
A. Biased, overstating the effectiveness of the diet.
The environmental protection agency records data on the fuel economy of many different makes of cars. They are interested in determining if one could predict the mileage of the care (in miles per gallon) from the weight of the car (in lbs). What is the response variable in this study? A. Mileage of the car B. Weight of the car C. Either mileage of the car or weight of the car; it doesnt matter
A. Mileage of the car
A researcher finds 2000 mildly overweight women who exercise regularly, have no had a heart attack, and are willing to participate in the study. She randomly assigns 500 of the women to take an appetite suppressant. The other 500 women are given a placebo. Both groups are following for 5 years and the amount of weight loss after this time is recorded. The response variable in this experiment is: A. The amount of weight loss B. The proportion of women in each group that stayed in the study C. Whether women exercised D. The age of the women
A. The amount of weight lost
Which of the following is true? A. The correlation, r, measures the strength of the linear relationship between two quantitative variables B. The correlation, r, measures the strength of the linear relationship between two categorical variables C. The correlation, r, measure the strength between one quantitative variable and one categorical variable D. When calculating the correlation, r, it is important to make sure x is the explanatory variable and the y is the response variable
A. The correlation, r, measures the strength of the linear relationship between two quantitative variables
Suppose that two very large companies (A and B) each select random samples of their employees. Company A had 5000 employees. Company B has 15,000 employees. In both surveys, the company will record the number of sick days taken by each sampled employee. If each company randomly selects 50 employees for the survey, which of the following is true about the sampling distributions of the sample means (the mean number of sick days)? A. The sampling distributions of the sample means will have about the same standard deviation. The standard deviation for a sampling distribution of a sample mean depends only on the sample size, not the population (company) size. B. Since Company A is surveying a higher percent of its employees, the standard deviation of the sampling distribution for its sample mean will be smaller than that for Company B (the larger company). Larger companies should take larger samples.
A. The sampling distributions of the sample means will have about the same standard deviation. The standard deviation for a sampling distribution of a sample mean depends only on the sample size, not the population (company) size.
Suppose that two very large companies (A and B) each select random samples of their employees. Company A had 5000 employees. Company B has 15,000 employees. In both surveys, the company will record the number of sick days taken by each sampled employee. If each firm randomly selects 3% of its employees, which of the following is true about the sampling distributions of the sample means? A. The standard deviation of the sampling distribution of the sample mean will be smaller for the larger company (Company B) because a larger sample is being selected B. The sampling distributions of the sample means will have about the same standard deviation since in both cases we're selecting 3% of the employees C. The smaller company (Company A) will have a sampling distribution with smaller standard deviation D. None of the above
A. The standard deviation of the sampling distribution of the sample mean will be smaller for the larger company (Company B) because a larger sample is being selected
Parts being manufactured at a plant are supposed to weigh 40 grams. Suppose the distribution of weights has a Normal distribution with mean 40 grams and standard deviation 2 grams. Quality control inspectors randomly select 16 parts, weigh each, and then compute the sample average weight for the 16 parts. The sampling distribution of the sample mean A. is exactly Normal with mean 40 grams and standard deviation 0.5 grams. B. is approximately Normal with mean 40 grams and standard deviation 0.5 grams.
A. is exactly Normal with mean 40 grams and standard deviation 0.5 grams.
Two variables in a study are said to be confounded if A. one cannot separate their effects on a response variable. B. they are highly correlated. C. they do not have a normal distribution. D. one of them is a placebo.
A. one cannot separate their effects on a response variable.
In order to investigate treatments for morbid obesity, obese subjects satisfying fairly strict requirements were randomly assigned to one of three groups: gastric bypass surgery; participation in a diet and exercise program; or both gastric bypass surgery and participation in the diet and exercise program. Researchers carefully observed the amount of weight lost five years after the study began. This study uses the principles of
A. randomization
In a study of human development, investigators showed two movies that were different types to groups of children. Crackers were available in a bowl, and the investigators compared the number of crackers eaten by children watching both movies. One movie was shown at 8 AM (right after the children had breakfast) and the other at 11 AM (right before the children had lunch). It was found that during the movie shown at 11 AM, more crackers were eaten than during the movie shown at 8 AM. The investigators concluded that the different types of movies had different effects on appetite. The response variable in this experiment is A. the number of crackers eaten. B. the different kinds of movies. C. the time each movie was shown. D. the bowls.
A. the number of crackers eaten.
In a large population of college-educated adults, the mean IQ is 112 with standard deviation 25. Suppose 300 adults from this population are randomly selected for a market research campaign. The distributions of the sample mean IQ is A. Approx. normal, mean 112, SD 25 B. Approx. normal, mean 112, SD 1.443 C. Approx. normal, mean 112, SD 0.083 D. Approx. normal, mean equal to the observed value of the sample mean, SD 25
B
According to the Current Population Survey, the following table summarizes probabilities for randomly selecting a full-time student in various age groups: Age 15-17 - .007 18-24 - .573 25-34 - .260 35 or older - .160 If we randomly select a full-time student, the probability that he/she is not 18-24 years old is A. 0.377. B. 0.427. C. 0.573. D. 0.993.
B. 0.427.
In a survey of sleeping habits, 8400 national adults were selected randomly and contacted by telephone. Respondents were asked, "typically how many times per week do you sleep less than 6 hours during the night?" On average, those surveyed reported an average of 1.8 nights per week in which they got less than 6 hours. Which of the following is true with respect to this scenario? A. 8400 is the size of the population being studied B. 1.8 is a statistic and represents an estimate of the unknown value of a parameter of interest C. 1.8 is a parameter and represents an estimate of the unknown value of a statistic of interest D. None of the above
B. 1.8 is a statistics and represents an estimate of the unknown value of a parameter of interest
A public opinion poll in Ohio wants to determine whether registered voters in the state approve of a measure to ban smoking in all public areas. The researches select a simple random sample of 50 registered voters from each county in the state and ask whether they approve or disapprove of the measure. This is an examples of: A. A systematic county sample B. A stratified sample C. A multistage sample D. A simple random sample
B. A stratified sample
Advice columnist Ann Landers once asked her readers with children to answer the following questions: "If you had it to do over again, would you have children?" Readers were invited to send a response to this question by mail. Of the approx. 10,000 responses Landers received, approx. 70% said "no." The population of interest is: A. The more than 10,000 people that responded B. All readers that are parents C. The readers with children that regret having children D. The children that are unwanted
B. All readers that are parents
A researcher is interested in determining if one could predict the score on a statistics exam from the amount of time spent studying for the exam. What is the explanatory variable in this study. A. Score on the exam B. Amount of time spent studying for the exam C. Either score on the exam or amount of time spent studying for the exam; it doesnt matter
B. Amount of time spent studying for the exam
Some researchers have noted that adolescents who spends a lot of time playing video or computer games are at greater risk for depression and for violence. This is an example of: A. A valid conclusion since more time yields more aggression is a positive association B. An observational study with lurking variables that may explain the association C. A single-blind experiment because the subjects knew they were watching television D. A paired data experiment since we are studying both aggression and TV watching
B. An observational study with lurking variables that may explain the association
The strength of the linear relationship between two numerical variables may be measured by the A. Scatter diagram B. Coefficient of correlation C. Slope D. Y-intercept
B. Coefficient of correlation
I toss a penny and observe whether it lands heads up or tails up. Suppose the penny is fair, i.e., the probability of heads is 1/2 and the probability of tails is 1/2. This means A. Every occurrence of head must be balanced by a tail in one of the next two or three tosses B. If i flip the coin many, many times, the proportion of heads will be approximately 1/2, and this proportion will tend to get closer and closer to 1/2 as the number of tosses increases C. Regardless of the number of flips, half will be heads and half tails D. All of the above
B. If i flip a coin many, many times, the proportion of heads will be approximately 1/2, and this proportion will tend to get closer and closer to 1/2 as the number of tosses increases
Which of the following statements about a scatterplot is (are) true? A. It is always necessary to identify one of the two variables as the explanatory variable and the other as the response variable. B. On a scatterplot we look for overall patterns showing the form, direction, and the shape of the relationship C. Because a scatterplot requires the values of two quantitative variables, it is never possible to add one or more categorical variables to the graph D. Both A and B are true E. None of the above
B. On a scatterplot we look for overall patterns showing the form, direction, and the shape of the relationship
Each month, the census bureau mails survey forms to 250,000 households asking questions about the people living in the household and about such things as motor vehicles and housing costs. Telephone calls are made to households that don't return the form. In one month, responses were obtained from 240,000 of the households contacted. The sample is: A. The 250,000 households initially contacted B. The 240,000 households that respond C. The 10,000 households that did not respond D. All U.S. households
B. The 240,000 households that respond
Suppose you're in a class of 35 students. The instructor takes simple random sample of 7 students and observes their heights. Imagine all of the different samples possible. Let X denote the tallest height in your sample. The distribution of all values taken by X in all possible samples of 7 students selected from the 35 students in your class is A. The probability that X is obtained B. The sampling distribution of X C. The standard deviation of values D. The parameter
B. The sampling distribution of X
A simple random sample of 1000 American adults found that the average number of hours spent watching television during a typical week was 13.8. A simple random sample of 500 Canadians yielded an average of 12.5 hours per week of television viewing. Assume that the American and Canadian distributions for weekly television, viewing times have the same standard deviations. The sampling variability associated with the sample means (described above) is A. smaller for the sample of Canadians since the population of Canada is less than half that of the United States. B. larger for the sample of Canadians because the sample size is smaller.
B. larger for the sample of Canadians because the sample size is smaller.
A political party sends a mail survey to 1500 randomly selected registered voters in a community. The survey asks respondents to give an opinion about the job performance of the current President. Of the 1500 surveys sent out, 480 are returned, and of these, only 120 say they're satisfied with the President's job performance. The sample is A. the 1500 randomly selected voters receiving the questionnaire. B. the 480 surveys returned. C. the 120 voters surveyed that are satisfied with the President's job performance. D. the voters in his district.
B. the 480 surveys returned.
A 1992 Roper poll found that 22% of Americans say that the Holocaust may not have happened. The actual question asked in the poll was "Does it seem possible or impossible to you that the Nazi extermination of the Jews never happened?" and 22% responded "Possible." The results of this poll cannot be trusted because A. undercoverage is present. Obviously, those people who did not survive the Holocaust could not be in the poll. B. the question is worded in a confusing manner. C. we do not know who conducted the poll or who paid for the results. D. nonresponse is present. Many people will refuse to participate, and those that do will be biased in their opinions.
B. the question is worded in a confusing manner.
When the explanatory variable is categorical and the response variable is quantitative, what type of the plot would be appropriate?
Boxplot
A call in poll conducted by a local radio station concluded A. Simple random sampling B. Stratified random sampling C. Volunteer sampling D. Multistage sampling
C
A political party send a mail survey to 1500 randomly selected registered voters A. A survey with little bias since people understand B. A survey with little bias because 1500 voters C. A survey containing non response D. All of the above
C
A manufacturing process produces bags of cookies. The distribution of content weights of these bags is Normal with mean 16.0 oz and standard deviation 0.8 oz. We will randomly select n bags of cookies and weigh the contents of each bag selected. How many bags should be selected so that the standard deviation of the sample mean is 0.1 ounces?
C. 64 bags
About 64% of boys aged 12-15 regularly play video games. If we select a single boy in this age group, the probability that he regularly plays video games A. About 17 B. About 0.83 C. About 0.64 D. None of the above
C. About 0.64
When examining a scatterplot for strength, you are looking to see A. How close the points in the scatterplot follow a line B. How close the points in the scatterplot follow a curve C. All of the above D. None of the above
C. All of the above
When looking for relationships between two quantitative variables, you are looking for _____ A. Linear relationships B. Nonlinear relationships C. All of the above D. None of the above
C. All of the above
Every 4 years, during the winter Olympic games, debates arise over whether figure skating judges are completely fair. The correlation coefficient between the scores given by the French judge and the Romanian judge is, as expected, positive: r=0.75. Does the French judge tend to give higher scores than the Romanian judge? A. Yes B. No C. Cannot be determined from the given information
C. Cannot be determined from the given information
The lack of a linear relationship between two quantitative variables is represented by the correlation, r, with values ___ A. Greater than zero B. Less than zero C. Equal to zero D. equal to 1 or -1
C. Equal to zero
A college newspaper interviews a psychologist about a proposed system for rating the teaching ability of faculty members. The psychologist says, "The evidence indicates that the correlation between a faculty members research productivity and teaching rating is close to zero." What would be a correct interpretation of this statement? A. Good researchers tend to be poor teachers and vice versa B. Good teachers tend to be poor researchers and vice versa C. Good researchers are just likely to be good teachers as they are bad teachers. Likewise for poor researchers. D. Good research and good teaching go together
C. Good researchers are just as likely to be good teachers as they are bad teachers. Likewise for poor researchers
To select a sample of undergraduate students in the United States, i select random sample of four states. For each of these states, i select a simple random sample of two colleges or universities. Finally, from each of these eight colleges or universities, i select a simple random sample of 20 undergraduates. My final sample consists of 160 undergraduates. This is an example of A. Simple random sampling B. Stratified random sampling C. Multistage sampling D. Convenience sampling
C. Multistage sampling
The correlation between length and width is calculated to be r=0.827. Suppose we removed the point that is indicated by a * from the data represented in the plot. What would the correlation between length and width then be? A. 0.827 B. Large than 0.827 C. Smaller than 0.827 D. Either larger or smaller than 0.827. It is impossible to say which
C. Smaller than 0.827
Which of the statements is true? A. The correlation, r, is always positive B. The correlation, r, is always negative C. The correlation, r, can be any number between -1 and 1 D. The correlation, r, measures the shape of a scatterplot
C. The correlation, r, can be any number between -1 and 1
Sickle-cell disease is a painful disorder of the red blood cells that in the United States affects mostly blacks. To investigate whether the drug hydroxyurea can reduce the pain associated with sickle-cell disease, a study by NIH gave the drug to 150 sickle-cell sufferers and the placebo to another 150. Neither doctors nor patients were told who received the drug. The number of episodes of pain reported by each subject was recorded. This is an example of A. an observational study. B. an experiment, but not a double-blind experiment. C. a double-blind experiment. D. a paired data experiment.
C. a double-blind experiment.
One hundred volunteers who suffer from agoraphobia are available for a study. Fifty are selected at random and are given the drug imipramine, which is believed to be effective in treating agoraphobia. The other 50 are given a placebo. A psychiatrist evaluates the symptoms of all volunteers after two months to determine if there has been substantial improvement in the severity of the symptoms. This study would be double-blind if
C. neither the volunteers nor the psychiatrist knew which subjects had received the placebo.
The central limit theorem says that when a simple sample of size n is drawn from any population with mean μ and standard deviation σ, then when n is sufficiently large A. the standard deviation of the sample mean is σ2/n. B. the distribution of the population is approximately Normal. C. the distribution of the sample mean is approximately Normal. D. the distribution of the sample mean is exactly Normal.
C. the distribution of the sample mean is approximately Normal.
To assess the opinion of students at the Ohio State University about campus safety, a reporter for the student newspaper interviews 15 students she meets walking on the campus late at night who are willing to give their opinion. The sample obtained is A. Simple random sample of students feeling safe B. Stratified random sample of students feeling safe C. Probability sample of students with night classes D. Probably biased
D
An electronics store is handing out a survey to their clients who buy a smartphone. Some of the questions on the survey ask the clients to rate the smartphone on ease of use, appearance, price, etc. Another question asks for the client's age. From all the different ratings on the survey, a total assessment score is calculated. The correlation between this total assessment score and age of the client is -0.165. The store owner can legitimately conclude which of the following? A. Older clients seem to not like smartphones B. There is a negative linear relationship between age and assessment score C. Age does not help much in predicting assessment score D. None of the above
D. None of the above
Medical researchers are excited about a new cancer treatment that destroys tumors by cutting off their blood supply. To date, the treatment has only been tried on mice, but in mice it has been nearly 100% effective. As evidence of the effectiveness of the new treatment in treating cancer in humans, these studies A. Display a high degree of statistical significance, and so with nearly 100% certainty will work in humans B. Are convincing, assuming the results have been replicated in a large number on mice C. Are convincing, assuming the results have been replicated in a large number of mice D. Suffer from lack of realism
D. Suffer from lack of realism
Which of the following statements regarding the correlation coefficient is true? A. The correlation coefficient equals the proportion of times that two variables lie on a straight line B. The correlation coefficient will be +1.0 if all the data points lie on a perfectly horizontal straight line C. The correlation coefficient measures the strength of any relationship that may be present between two variables D. The correlation coefficient is a unitless number and must always lie between -1.0 and +1.9 inclusive
D. The correlation coefficient is unitless number and must always lie between -1.0 and +1.0 inclusive
A north american roulette wheel has 38 slots, of which 18 are red, 18 are black, and 2 are green. Suppose you decide to bet on red on each of 10 consecutive spins of the roulette wheel. Suppose you lose all 5 of the first wagers. Which of the following are true? A. You should get more spins of red on the next 5 spins of the wheel, since we didnt get any on the first 5 spin B. The wheel is not working properly. It favors outcomes that are not red. Hence, during the next five spins of the wheel, we're likely to continue to see few red outcomes C. We're due for a win, so the sixth spin of the wheel is very likely to come up red D. What happened on the first 5 spins tells us nothing about what will happen on the next 5 spins
D. What happened on the first 5 spins tells us nothing about what will happen on the next 5 spins
The number of column inches of classified advertisements appearing on Mondays in a certain daily newspaper has mean 320 inches and standard deviation 30 inches. Suppose that the results for 100 consecutive Mondays can be regarded as a random sample and let denote the mean number of column inches of classified advertisements in the sample. Assuming a sample of 100 is sufficiently large, the random variable has
D. all of the above
In a study of human development, investigators showed two movies that were different types to groups of children. Crackers were available in a bowl, and the investigators compared the number of crackers eaten by children watching both movies. One movie was shown at 8 AM (right after the children had breakfast) and the other at 11 AM (right before the children had lunch). It was found that during the movie shown at 11 AM, more crackers were eaten than during the movie shown at 8 AM. The investigators concluded that the different types of movies had different effects on appetite. The results cannot be trusted because A. the study was not double-blind. Neither the investigators nor the children should have been aware of which movie was being shown. B. the investigators were biased. They knew beforehand what the study would show. C. the investigators should have used several bowls, with crackers randomly placed in each. D. the time each movie was shown is a confounding variable.
D. the time each movie was shown is a confounding variable.
When examining a scatterplot for form, you are looking to see if ____? A. The points in the scatterplot show a straight line pattern B. The points in the scatterplot show a curved relationship C. There are clusters in the scatterplot D. None of the above E. A, B, and C
E. A, B, and C
An experimenter is studying the bonding strength of adhesives that contain varying amounts of a particular chemical additive. Wafers of a specified material are glued together using the adhesive with each amount of additive, allowed to sure for 24 hours, and then the strength needed to separate the wafers is determined. It is reported that the correlation between strength required and amount of additive was 0.86 pounds-force per square inch. The report is ___ because correlation ____
Incorrect; is unitless
Volunteers for a research study were divided into three groups. Group 1 listened to Western religious music, Group 2 listened to Western rock music, and the change in blood pressure (blood pressure before listening minus blood pressure after listening) was recorded. What could we do to explore the relationship between type of music and change in blood pressure?
Make side-by-side boxplots of the change in blood pressure, with a separate boxplot for each group
Nationwide, the amount charged by doctors for performing a particular minor surgical procedure averages $1220 and varies with a standard deviation of $300. We randomly select 160 bills from the population of all bills charged for this surgery. Let x bar represent the average amount charged for these 160 surgical procedures. The mean and standard deviation of the average x bar are
Mean = $1220 Standard dev. = $23.72
Two variables in a study are said to be confounded if?
One cannot separate their effects on a response variable
Do heavier cars use more gasoline? A researcher randomly selected 15 cars. He collected data about the weight (in hundreds of pounds) and the mileage (mpg) for each car. From a scatterplot made with data, a linear model seems appropriate. What is the explanatory variable in this study?
Weight
