statistics final

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 probability that the sample mean IQ is greater than 115 is: ______(Round your answer to three decimal places.)

.019

The average age of residents in a large residential retirement community is 69 years with standard deviation 5.8 years. A simple random sample of 100 residents is to be selected, and the sample mean age x̄ of these residents is to be computed. The probability that the average age, x̄ of the 100 residents selected is less than 68.5 years is: _____ (Round your answer to two decimal places. Note that a probability is a number between 0 and 1.)

.19

For a certain hospital, the average birth weight for babies born there was 119.6 ounces with a standard deviation of σ = 6.5 ounces. Assume that in the population of all babies born in this hospital, the birth weights follow a normal distribution, with mean µ. Suppose we take simple random samples of size 25 from the set of baby weights from this hospital. The standard deviation of the sampling distribution of the mean is: (round to one decimal place) ______ ounces

1.3

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 distribution of the sample mean IQ is approximately normal with mean: _________ standard deviation: ______

112 . 1.44

A random sample of n = 25 flights was taken and the time recorded to board the flight. It was found that the sample mean, x̄ = 42 minutes. Previous studies had determined boarding times to be normally distributed with µ = 38 minutes and σ = 36 minutes. The sampling distribution of x̄, the sample average in samples of size n = 25 is normal with mean: _____ standard deviation: ______ Round the mean to a whole number and the standard deviation to one decimal places.

38 . 7.2

Sickle-cell disease is a painful disorder of the red blood cells that in the United States affects mostly African Americans. To investigate whether the drug hydroxyurea can reduce the pain associated with sickle-cell disease, a study by the NIH gave the drug to 150 sickle-cell sufferers and 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 an observational study. an experiment, but not a double-blind experiment. a double-blind experiment. a paired data experiment.

a double-blind experiment.

A public opinion poll in Ohio wanted to determine whether registered voters in the state approved of a measure to ban smoking in all public areas. The researchers selected a simple random sample of 50 registered voters from each county in the state and asked whether they approved or disapproved of the measure. This is an example of a systematic county sample. a stratified sample. a multistage sample. a simple random sample.

a stratified sample.

what kind of study Deliberately imposes a treatment on individuals and record their responses. Influential factors can be controlled.

experimental

Apparently, according to some studies, men that drive expensive sports cars have lower blood pressure and fewer cardiovascular health problems. We can't conclude that driving expensive sports cars lowers blood pressure or improves cardiovascular health because the studies described are clearly experiments. observational studies, not experiments—lurking variables may explain the association. paired data experiments. stratified experiments.

observational studies, not experiments—lurking variables may explain the association.

A student asks each person in one of his classes how many hours, on average, they spend studying each week. This is an example of convenience sampling. a double-blind experiment. a simple random sample. voluntary response sampling.

convenience sampling.

is a number describing a characteristic of the population

parameter

The mean of the sampling distribution is the same as that of the

parent population

A lot of 10,000 ball bearings has a mean diameter of 2.503 centimeters. An inspector randomly chooses 100 of them and finds they have a mean diameter of 2.515 centimeters. The number 2.503 centimeters is a population parameter. statistic.

population parameter.

In a study of all 2223 passengers aboard the Titanic, it was found that 31.8% survived when it sank. The number 31.8% is a population parameter. statistic

population parameter.

The national median age of people in the US was 38,1 years in 2018 The number 38.1 years is a population parameter. statistic.

population parameter.

Which of the following groups are subject to coercion to participate in a clinical trial by other persons with the power to impose punishment for refusal to participate? adults with a serious illness. parents of children, if the parent is against participation but the child is not. prisoners. All of the choices are correct.

prisoners.

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. a stratified random sample of students feeling safe. a probability sample of students with night classes. probably biased.

probably biased.

Informed consent refers to asking the patient to sign a form that they agree to participate in a clinical trial. outlining to the patient how the study will be conducted. providing the patient with a detailed description of the study, including all benefits and risks and asking for written consent. None of the choices are correct.

providing the patient with a detailed description of the study, including all benefits and risks an

what kind of sampling: rely on the absolute objectivity of random numbers. There are books and tables of random digits available for random sampling

random

Sampling _________ gets rid of bias.

randomly

Questions about the past or sensitive issues often get biased responses ("How much do you drink?" or "How much do you weigh?" ).

response bias

Researchers have noted that children who learn to play a musical instrument through taking lessons have higher average SAT scores, higher average GPA, and higher average class rank. The various measures of academic success described are examples of explanatory variables. response variables. confounding variables. None of the choices are correct.

response variables.

is an observational study that relies on a random sample drawn from the entire population .

sample survey

taking a histogram of many many sample averages

sampling distribution

what kind of sampling: is made of randomly selected individuals. Each individual in the population has the same probability of being in the sample. All possible samples of size n have the same chance of being drawn.

simple random sample

The sampling distribution of a statistic is the probability that we obtain the statistic in repeated random samples. the mechanism that determines whether randomization was effective. the distribution of values taken by a statistic in all possible samples of the same size from the same population. the extent to which the sample results differ systematically from the truth.

the distribution of values taken by a statistic in all possible samples of the same size from the same population.

The Excite Poll is an online poll at poll.excite.com. You click on an answer to become part of the sample. One poll question was "Do you prefer watching first-run movies at a movie theater, or waiting until they are available on home video or pay-per-view?" A total of 8896 people responded with 1118 saying they preferred theaters. From this survey you should conclude that Americans prefer watching movies at home. a larger sample is necessary. the poll uses voluntary response, so the results tell us little about the population of all adults. movie theaters should lower their prices.

the poll uses voluntary response, so the results tell us little about the population of all adults.

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 undercoverage is present. Obviously, those people who did not survive the Holocaust could not be in the poll. the question is worded in a confusing manner. we do not know who conducted the poll or who paid for the results. nonresponse is present. Many people will refuse to participate, and those who do will be biased in their opinions.

the question is worded in a confusing manner.

Suppose you're in a class of 35 students. The instructor takes a simple random sample of seven 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 seven students selected from the 35 students in your class is the probability that X is obtained. the sampling distribution of X. the statistic. the parameter.

the sampling distribution of X.

Suppose you interview 10 randomly selected workers and ask how many miles they commute to work. You'll compute the sample mean commute distance. Now imagine repeating the survey many, many times, each time recording a different sample mean commute distance. In the long run, a histogram of these sample means represents the bias, if any, that is present in the sampling method. the true population average commute distance. a simple random sample. the sampling distribution of the sample mean.

the sampling distribution of the sample mean.

The standard deviation of the sampling distribution is equal to

the standard deviation of the parent population divided by the square root of n

Two variables (explanatory or lurking variables) are ___________ when their effects on a response variable cannot be distinguished from each other.

confounding

A placebo is an important element of many clinical trials because it serves as a control for the experiment. it allows the researcher to adjust for psychological effects of receiving medical attention. use of the placebo can help avoid confounding. All of the choices are correct.

All of the choices are correct.

During the 1936 presidential election between Franklin D. Roosevelt and Alf Landon, the Literary Digest received 2.3 million mail-in ballots that it used to predict the results: a landslide in favor of Landon. Clearly, there has never been a President Landon, so the prediction was incorrect. Why? A sample taken only from Literary Digest readers would not necessarily represent the views of the American public in general. The survey relied on voluntary responses, which would introduce a bias. The survey was subject to nonresponse bias. All of the choices are correct.

All of the choices are correct.

In order to investigate treatments for morbid obesity, obese subjects satisfying fairly strict requirements were randomly assigned to one of three groups: (1) gastric bypass surgery, (2) participation in a diet and exercise program, or (3) both gastric bypass surgery and participation in the diet and exercise program. This clinical trial is ethical because all subjects are likely to receive benefits. randomization is ethical if no treatment seems to work better than the others. interests of the study subjects prevail. All of the choices are correct.

All of the choices are correct.

There were 5317 previously owned homes sold in a western city in the year 2000. The distribution of the sale prices was strongly right-skewed, with a mean of $206,274 and a standard deviation of $37,881. If we take many simple random samples of size 100 from this population and calculate the mean for each sample, which of the following describes the sample distribution of the sample mean? Approximately normal with mean $206,274 and standard deviation $3,788. Approximately normal with mean $206,274 and standard deviation $3,7881. Approximately normal with mean $206,274 and standard deviation $520. Strongly right-skewed with mean $206,274 and standard deviation $3788. Strongly right-skewed with mean $206,274 and standard deviation $37881.

Approximately normal with mean $206,274 and standard deviation $3,788.

what do confidence intervals do

Estimate the value of a population parameter Give a range for the population parameter

use multiple stages of stratification. They are often used by the government to obtain information about the U.S. population.

Multistage samples

One hundred sixty people who suffer from painful diabetic neuropathy have volunteered to participate in a study. Eighty are selected at random and are given the drug gabapentin, which (although originally intended to prevent epileptic seizures) has properties that may make it useful to alleviate neuropathy. The remaining participants are given a placebo. A neurologist evaluates the symptoms of all volunteers after two months to determine if there has been substantial improvement in the severity of the symptoms. Does the use of volunteers make this study invalid? Yes, because of volunteer bias. Yes, because there is no way to determine the effect of gabapentin on people that do not have symptoms of neuropathy. No, because the subjects are randomly assigned to treatment groups. No, because blocking was used.

No, because the subjects are randomly assigned to treatment groups.

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. This is an example of a survey with little bias because an individual will know for certain whether they approve of the President's job performance. a survey with little bias because 1500 voters represent an important part of his district. a survey with no bias. None of the choices are correct.

None of the choices are correct.

When a felony convict is released from prison, the person is often placed on parole for some time. During parole, the person can be returned to prison by the supervising parole agent without a trial and conviction. A criminologist plans a randomized study comparing an intervention with a regular release from prison to study the effectiveness of the intervention in preventing re-incarceration. The criminologist prepares an informed consent form and plans to enroll parolees during the first meeting with the parole agent who will introduce the study to the parolee. The procedure is appropriate because parolees are adults and are free to participate or not. there are no risks to the parolee, only potential benefits. the parole agent has the best interest of the parolee in mind and will advise accordingly. None of the choices are correct.

None of the choices are correct.

The entire group of individuals in which we are interested but can't usually assess directly

Population

the part of the population we actually examine and for which we do have data

Sample

The distribution of actual weights of 8-ounce wedges of cheddar cheese produced at a dairy is normal with mean 8.1 ounces and standard deviation 0.2 ounces. In previous work, the dairy used random samples of size 10 for quality assurance. The company decides instead to sample batches of 20 cheese wedges. How will the distribution of the sample means of the weights of cheese wedges with sample sizes of 20 change from the previous batches, which only contained 10 samples? The shape of the distribution may change completely based on the new data. The distribution will still be normal, but it will be more peaked around the sample mean and the standard deviation will be smaller. The distribution will still be normal, but it will be less peaked around the sample mean and the standard deviation will be larger. It is not possible to tell from the information provided.

The distribution will still be normal, but it will be more peaked around the sample mean and the standard deviation will be smaller.

what kind of sampling: Just ask whoever is around

convenience sampling

For a certain hospital, the average birth weight for babies born there was 119.6 ounces with a standard deviation of σ = 6.5 ounces. Assume that in the population of all babies born in this hospital, the birth weights follow a normal distribution, with mean µ. In the previous question, we considered simple random samples of size 25. If the sample size of birth records increases, how does the sampling distribution change? The shape of the distribution will change, but it is dependent upon the new data that is collected. The sampling distribution will remain normal and the mean will remain the same regardless of the sample size, but its standard deviation will be larger than the sampling distribution based on the smaller sample. The sampling distribution will remain normal regardless of the sample size, and will have the same average and standard deviation as the sampling distribution computed from the smaller sample. The sampling distribution will remain normal and the mean will remain the same regardless of the sample size, but its standard deviation will be smaller than the sampling distribution based on the smaller sample.

The sampling distribution will remain normal and the mean will remain the same regardless of the sample size, but its standard deviation will be smaller than the sampling distribution based on the smaller sample.

Suppose that two very large companies (A and B) each select random samples of their employees. Company A has 5000 employees and 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)? 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. Since Company A is surveying a higher percent of its employees, the standard deviation of the sampling distribution for its sample mean will be significantly smaller than that for Company B (the larger company). Larger companies should take larger samples. Since Company B is a larger company, the standard deviation for its sampling distribution of the sample mean is signficantly smaller. The larger a population, the smaller the standard deviation of a sample mean's sampling distribution. None of the above.

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 has 5000 employees and 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? 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. The sampling distributions of the sample means will have about the same standard deviation because in both cases we're selecting 3% of the employees. The smaller company (Company A) will have a sampling distribution with smaller standard deviation. None of the above.

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.

describes the mean, SD, and shape of sampling distributions

central limit theorem

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 population is the 1500 registered voters in the community selected to receive this survey. the 480 respondents that answered the survey. the 120 respondents satisfied with the President's job performance. all registered voters in this community.

all registered voters in this community.

Some researchers have noted that adolescents who spend a lot of time playing video or computer games are at greater risk of depression and violence. This is an example of a valid conclusion because more time yields more aggression is a positive association. an observational study with lurking variables that may explain the association. a single-blind experiment because the subjects knew they were watching television. a paired data experiment because we are studying both aggression and TV watching.

an observational study with lurking variables that may explain the association.

Researchers have noted that children who learn to play a musical instrument through taking lessons have higher average SAT scores, higher average GPA, and higher average class rank. This is an example of an experiment. an observational study. the establishing of a causal relationship through correlation. a block design, with music and no-music groups as blocks.

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 an observational study. a multistage sample. a double-blind experiment. a block design.

an observational study.

If n is large, then the sampling distribution is __________, even if the distribution of parent population is not normal.

approximately normal

The shape of a sampling distribution of a proportion is not _________ in general

normal

what study enlist individuals with a common demographic feature and keep track of them over a long period of time. When the study is over, individuals who have developed a condition are then compared with the remaining, unaffected individuals.

cohort studies

what kind of study starts with two random samples of individuals with different outcomes and look for exposure factors in the subjects' past that differ between the two groups

case control studies

if the distribution of the parent population is normal, then the sampling distribution is _____________ regardless of the sample size n.

normal

what kind of study Records data on individuals without attempting to influence the responses. Interpretation of results may be confounded with possible lurking variables

observational

At 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 affect 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 approach is an observational study. an experiment, but not a double-blind experiment. a double-blind experiment. fundamentally flawed because only a well-designed experiment with randomized assignment to treatments can be used to determine a cause-and-effect relationship.

fundamentally flawed because only a well-designed experiment with randomized assignment to treatments can be used to determine a cause-and-effect relationship.

Advice columnist Ann Landers once asked her readers with children to answer the following question: "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 approximately 10,000 responses Landers received, approximately 70% said "no." The sample is probably representative of all parents. is probably not representative of all parents because people who feel very strongly about this issue are more likely to respond than people who do not. has little bias because more than 10,000 people responded, yielding a very large sample. is probably not representative because more than 10,000 people responded.

is probably not representative of all parents because people who feel very strongly about this issue are more likely to respond than people who do not.

what we mean by 95%

is that if we were to repeat the entire process of taking a random sample of size -and forming a confidence interval from each sample in the same as we did in this case many times, then the entire collection of intervals we would create would contain the mean - for all -who are treated this way.

To select a sample of undergraduate students in the United States, I select a simple random sample of four states. From 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 simple random sampling. stratified random sampling. multistage sampling. convenience sampling.

multistage sampling.

One hundred sixty people who suffer from painful diabetic neuropathy have volunteered to participate in a study. Eighty are selected at random and are given the drug gabapentin, which (although originally intended to prevent epileptic seizures) has properties that may make it useful to alleviate neuropathy. The remaining participants are given a placebo. A neurologist 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 neither drug had any identifying marks on it. neither the volunteers nor the neurologist were allowed to see each other during the session during which the neurologist evaluated the severity of the symptoms. neither the volunteers nor the neurologist knew which subjects had received the treatment and which had received the placebo. All of the choices are correct.

neither the volunteers nor the neurologist knew which subjects had received the treatment and which had received the placebo.

People who feel they have something to hide or who don't like their privacy being invaded probably won't answer. Yet they are part of the population.

nonresponse bias

The Bureau of Labor Statistics announced that last month it interview all member of the labor force in a sample of 60,000 US households; 4.9% of the people interviewed were unemployed. The number 4.9% is a population parameter. statistic

statistic

is a number describing a characteristic of a sample

statistic

A lot of 10,000 ball bearings has a mean diameter of 2.503 centimeters. An inspector randomly chooses 100 of them and finds they have a mean diameter of 2.515 centimeters. The number 2.515 centimeters is a population parameter. statistic.

statistic.

what kind of sampling: is essentially a series of SRS performed on subgroups of a given population. The subgroups are chosen to contain all the individuals with a certain characteristic.

stratified random sample

A student organization wanted to study voting preferences in its student body during the 2012 presidential election. They selected 120 students at random from each class, freshmen through seniors. The sampling technique being used is simple random sampling. stratified random sampling. volunteer sampling. multistage sampling.

stratified random sampling.

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 used on mice, but in mice it has been nearly 100% effective in eradicating tumors and appears to have no side effects. As evidence of the effectiveness of the new treatment in treating cancer in humans, these studies display a high degree of statistical significance, and so itwill work in humans with nearly 100% certainty. are convincing, assuming the results have been replicated in a large number of mice. are convincing, assuming that proper randomization and control were used. suffer from lack of realism.

suffer from lack of realism.

The average age of residents in a large residential retirement community is 69 years with standard deviation 5.8 years. A simple random sample of 100 residents is to be selected, and the sample mean age x̄ of these residents is to be computed. We know the random variable x̄ has approximately a normal distribution because of the central limit theorem. the law of large numbers. the 68-95-99.7 rule. the population from which we're sampling has a normal distribution.

the central limit theorem.

In a study of human development, investigators showed two different types of movies 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 A.M. (right after the children had breakfast) and the other at 11 A.M. (right before the children had lunch). It was found that during the movie shown at 11 A.M., more crackers were eaten than during the movie shown at 8 A.M. The investigators concluded that the different types of movies had different effects on appetite. The results cannot be trusted because the study was not double blind. Neither the investigators nor the children should have been aware of which movie was being shown. the investigators were biased. They knew beforehand what the study would show. the investigators should have used several bowls, with crackers randomly placed in each. the time each movie was shown is a confounding variable.

the time each movie was shown is a confounding variable.

A randomized placebo-controlled clinical trial may be conducted if medical science will benefit and there is minimal harm to humans, though no benefits to current patients. there is reason to hope the treatment will help patients who are subjects in the trial . there is strong evidence that the treatment works and the clinical trial will confirm it. All of the choices are correct.

there is reason to hope the treatment will help patients who are subjects in the trial .

Sometimes parts of the population are left out in the process of choosing the sample

undercoverage bias

what kind of sampling: individuals choose to be involved. These samples are very susceptible to being biased because different people are motivated to respond or not. They are often called "public opinion polls" and are not considered valid or scientific.

voluntary response sampling

what we say by 95%

we are 95% confidence that the interval -to -contains the mean - for all -under this condition

the wording is messed up in the survey

wording bias

In order for a sampling distribution to be non-normal,

you need to take small samples and the parent population needs to be non-normal. Note that both of these conditions must hold. Our second example had both.