DMC Exam 1 Prep

Which one of the following variables is not categorical?

Age

Choose the best answer that identifies any potential lurking variables in the following statement: There is a strong positive correlation between the foot length of K-12 students and reading scores.

Age/Grade level

Which of the following is true of a long string of digits 0,1,2,3,4,5,6,7,8,9 produced by software that generates random digits or listed in a table of random digits?

All answer choices are true.

Which of the following is an important weakness of the experiment described in the prior question?

Because undergraduate students were used as subjects and knew what was going on, the results may not generalize to everyday television viewers.

Is the following question biased or unbiased? "Do you prefer the ease of shopping online or the fun of going to a mall?"

Biased

The American Nurses Association wanted to gather information about the working environment for nurses in hospitals. A survey for nurses was posted on the association's website. Will this sampling method more likely result in a biased or unbiased sample?

Biased

Two mouthwash manufacturers claim that 4 out of every 5 dentists use only their brand. Both manufacturers can support their claims with survey results. Which of the following explanations could show why this seemingly contradictory result is possible? Select all that apply.

Biased samples of dentists already favoring one brand or another may have been used. Biased questions misleading dentists into answering a particular way may have been used.

Select the true statement about confounding variables.

Confounding variables may influence the response variable.

Select the true statement(s) about confounding variables.

Confounding variables may influence the response variable.

Which of the following can be inferred from a well-constructed in a confidence statement?

Level of Confidence, Margin of Error, and Sample Size

Which of the following reasons may explain why someone may want to use biased questions in a survey?

None

Which of the following statements are true? I. Random sampling is a good way to reduce response bias .II. To guard against bias from undercoverage, use a convenience sample. III. Increasing the sample size tends to reduce survey bias.IV. To guard against nonresponse bias, use a mail-in survey.

None

are errors not related to the act of selecting a sample from the population.

Nonsampling errors

The following variable was used in the study. Is it numerical, categorical, or neither? Age

Numericial

Complete the analogy: population: __________ :: sample: __________

Parameter/statistic

Choose the best answer that identifies any potential lurking variable(s) in the following statement: Students who use tutors have lower test scores than students who do not.

Pre-tutoring test scores

Which of the following would be considered unethical in an experiment? Check all that apply.

Promising confidentiality to subjects but failing to protect it Failure to obtain informed consent from subjects Placing the interests of science over the interests of patients

is the deviation between the sampling statistic and the population parameter.

Random Sampling Error

What are the key ideas needed for the results of an experiment to be valid? Select all that apply.

Randomization, Control of variables, Large Sample Size

Bias occurring in the collection of a sample because of confusing questions in a questionnaire is classified as

Response Bias

Internet surveys, call-in surveys, and newpaper surveys often suffer from what kind of survey issues? Select all that apply.

Response, error, undercoverage, non-random samples

___________________ are errors caused by the act of taking a sample.

Sampling Errors

Chipotle Mexican Grill, an American chain of fast casual restaurants, is considering marketing shrimp as a new protein option for their burrito bowls. They will be using food taste testers to collect data and decide whether shrimp should be introduced. A variety of shrimp flavors are being tested (steamed, grilled, lime-cilantro, and Old Bay). Taste testers will rate their enjoyment of each flavor profile using a 1 to 5 Likert Scale (1- Gross! to 5- Delicious!). What is the explanatory variable?

Shrimp flavor

The basic type of random sample is the ______ _______ ______ which gives all samples of the same size the same change to be the sample we actually choose.

Simple random sample

Statistically significant is also called what according to the text?

Statistically Dissimilar

In general, if the population size were increased, but the sample size of the simple random sample stays the same, what would happen to the variability of the statistic?

Stay the same

There are approximately 3.9 Million registered voters in Maryland (as of September 2008, Baltimore Sun**) . How does the population size impact the level of confidence and consequently the margin of error?

The population size does not impact the level of confidence or the margin of error.

Comment on what is wrong with the following example survey questions: "What can we do to make the campus safer?"

The question implies that the campus is not safe.

A magazine printed a survey in its monthly issue and asked readers to fill it out and send it in. In the survey, the magazine asked for basic feedback on content in the magazine, overall layout, and reviews of customer service. Over 1000 readers replied. The results are not trustworthy as this survey suffers from:

Voluntary Response

The Denver Police Department wants to know if Hispanic residents of Denver believe that the police use racial profiling when making traffic stops. A sociologist prepares several questions about the police. The police department chooses an SRS of 200 mailing addresses in predominantly Hispanic neighborhoods and sends a uniformed Hispanic police officer to each address to ask the questions of an adult living there. The bias is

Voluntary Response Bias

If a researcher is interested in knowing how subjects who suffer from migraine headaches will feel if given an ibuprofen, then the explanatory variable is...

Whether or not an ibuprofen is taken.

A researcher is interested in studying the effect that living near a major roadway has on lung capacity. He finds a relationship between low lung capacity and living near a major roadway, but he finds that age affects both variables. What variables are confounded in this study?

age and living near a major roadway

Select all options that apply to randomized comparative experiments.

are subject to the laws of chance allows us to draw cause-and-effect conclusions. can draw stronger conclusions with smaller sample sizes compared to observational studies.

Convenience samples and voluntary response samples are ____________ in that they systematically favor some parts of the population over other in choosing the sample.

biased

A town council wants to know if residents support having an off-leash area for dogs in the town park. Eighty dogs owners are surveyed at the park. This is an example of what kid of sample? Is the sample biased or unbiased?

biased convenience sample

The following variable was used in the study. Is it numerical, categorical, or neither? Gender

categorical

The variable "whether or not they held a crocodile" was used in the study. Is it numerical, categorical, or neither?

categorical

A researcher is looking up area rainfall data for the summer (in centimeters) and attempting to understand how that impacts the crop yield for kale (in kilograms) grown at a local farm. What is the appropriate explanatory variable?

centimeters of rainfall

The school newspaper wants to find the opinions of students on availability of campus parking. They send a staff member to stand outside a busy dorm and interview students as they walk in or out of the building. Identify the study type.

convenience sample

A doctor wants to study the effect of a new medicine on headaches. She gives each participant either the medicine or a placebo, and neither the participant nor the doctor know whether the participant receives the medicine or a placebo.What design characteristic does this experiment have?

double-blind

In a ____________ experiment, neither the subject nor the people who work with them know which treatment each subject is receiving.

double-blind

What type of study controls for the preconceptions of both the researcher and the subject?

double-blind

A teacher is interested to know if the number of hours that a student spends doinghomework has an effect on the grade that a student earns on his or her exam. The number of hours that a student spends doing homework is an example of a(n)....?

explanatory variable

True or False: In every experiment, it is always possible to make the experiment double blind.

false

True or False: An experiment must have exactly one explanatory variable.

false

If a researcher is interested in knowing how subjects who suffer from migraine headaches will feel if given an ibuprofen, then the response variable is...

how much headache relief the subject experiences

Clinical trials are medical experiments performed on....?

human subjects

A method for selecting a sample is said to be biased if

it systematically favors certain outcomes.

A researcher is looking up area rainfall data for the summer (in centimeters) and attempting to understand how that impacts the crop yield for kale (in kilograms) grown at a local farm. What is the appropriate response variable?

kilograms of kale

Larger random samples have _____ variability than/as smaller samples.

less

Which is an example of response error?

lying in a survey.

By surveying only by telephone, the Goucher Poll contains what kind of error or bias?

non-response and undercoveragre

The following variable was used in the study. Is it numerical, categorical, or neither? Trials played on the EGM

numerical

A camp counselor at a sleep away camp gives any camper who is homesick and wants to go home a single pill of "homesick medicine." After 15 minutes, the kids always feel better and no longer want to go home. The "homesick medicine" is a tic-tac. This is an example of what?

placebo effect

An old professor is so cold one night that his usual blanket is not enough to warm him. He finally becomes warm after using his heated electric blanket, but awakes to discover that he had not plugged it in! What is the professor's experience an example of?

placebo effect

A city developer wants to determine whether a robotic bird is an effective means of warding off birds in a large urban area. He divides the city into structurally similar areas. In half of these areas, he releases the bird for two hours a day. Using cameras, he counts the number of birds present throughout the day in each location. What is the explanatory variable in this experiment?

presence of the robotic bird

Mistakes in handling data, such as arithmetic or data entry typos, is a nonsampling error known as ____________ error.

processing

Computing the margin of error when using a statistic to estimate a parameter is:

quantifying how much the statistic would vary from sample to sample

What does RDD stand for?

random digit dialing

You go to a website to access a news story. In order to access the story you are asked to answer a brief survey. If you choose not to answer the survey, you can only access the article for a fee. This method of obtaining a sample is an example of

random sampling, but not simple random sampling, because people visit the website at random.

A university wants to determine whether installing signs next to recycling containers has increased the amount of waste recycled. Students analyze recycling behavior by watching people dispose of trash in areas with and without recycling signs. If an observer makes it obvious that she is watching the behavior of a participant, what type of error would be present?

response

What does making a study double-blind help protect against?

response bias

A teacher is interested to know if the number of hours that a student spends doinghomework has an effect on the grade that a student earns on his or her exam. A student's grade on the exam is an example of a(n)...?

response variable

A researcher distributes a survey concerning smoking and heart disease to 1000 randomly chosen participants. She will analyze the results to try to establish a link between smoking and heart disease. What type of study is this?

sample survey

We select a _____ to get information about a _________

sample/population

A good sampling method has:

small bias and small variability.

An experiment that claimed to show that meditation reduces anxiety proceeded as follows. The experimenter interviewed the subjects and rated their levels of anxiety. The subjects were randomly assigned to two groups. The experimenter taught one group how to meditate, and they meditated daily for a month. The other group was simply encouraged to relax more. At the end of the month, the experimenter interviewed all the subjects again and rated their anxiety level. The meditation group had a greater decrease in anxiety than the group told to relax more. The results might be biased because:

the anxiety ratings at the end of the experiment should have been performed by someone blinded to which treatment a subject received.

Scientists are studying an endangered species, of which there are known to be about 100 remaining. Instead of tracking down each of the 100 animals, the scientists collect information from a sample of the population. Which of the following options is a possible sample size?

10

1833 bomber planes go out on a mission over enemy territory. 1002 of them come back. A statistician is asked to analyze the damage on these planes in order to determine which areas of the plane need better armor. To do this, the 1002 planes are each assigned a number from 1 to 1002. Then, 100 numbers between 1 and 1002 are randomly selected, and the corresponding planes are investigated for damage. It is found that 73% of the planes have significant damage to a particular section. What is the margin of error?

10%

Given a study with sample size n, what is the margin of error?

1\sqrt(n)

Consider the three situations:I. You ask a sample of doctors about the health risks involved with going out in the cold without a jacket.II. On cold days, you record which of your classmates come to school without a jacket. Later, you record how many of those students become sick. You take notes and observe at a local gym your fellow members who go outside with a wet head and notice if they are sick when they return to the gym at a later date.III. You find 30 adults and divide them into two groups. The first group is told not to wear jackets on cold days, the other group is told to wear jackets on cold days. You then compare the number from each group who get sick after a string of cold days. Which of the following situations is an example of an observational study?

2

A survey claims that the percent of a city's residents that favor recalling the corrupt mayor is likely between 82.3% and 95.5%. Approximately how many people were surveyed? Enter your answer to the nearest integer.

230

In general, to cut the margin of error in half we must use a sample _____ times as large.

4

Anonymity in a statistical study is

A bad idea if researchers want to follow up with subjects

How does a biased sample differ from a biased question?

A biased sample under- or over-represents part of the population by choosing less or more members from that part of the population, regardless of whether the survey is well-written. A biased question leads the respondent to favor certain answers by way of wording within the survey, regardless of whether the sample used is representative of the population.

What is one of the distinctions between a population parameter and a sample statistic?

A sample statistic changes each time you try to measure it, but a population parameter remains fixed.

Chipotle Mexican Grill, an American chain of fast casual restaurants, is considering marketing shrimp as a new protein option, for their burrito bowls. They will be using food taste testers to collect data and decide whether shrimp should be introduced. A variety of shrimp flavors are being tested (steamed, grilled, lime-cilantro, and Old Bay ® ). Taste testers will rate their enjoyment of each flavor profile using a 1 to 5 Likert Scale (1- Gross! to 5- Delicious!). What is the response variable?

Enjoyment level

A "randomized" experiment aims to

Ensure the placebo effect operates equally on all groups

A researcher wants to conduct a study to find the proportion of pet owners that vaccinate their pets. To create her simple random sample from a list of all registered cat and dog owners on file she chooses every third person on the list to contact. True or False: This sample is an example of a simple random sample.

False

True or False: Confidentiality is the same as anonymity.

False

Suppose you have high margin of error. What must necessarily also be true?

High variability

The Denver Police Department wants to know if Hispanic residents of Denver believe that the police use racial profiling when making traffic stops. A sociologist prepares several questions about the police. The police department chooses an SRS of 200 mailing addresses in predominantly Hispanic neighborhoods and sends a uniformed Hispanic police officer to each address to ask the questions of an adult living there. The population is:

Hispanic residents of Denver

I plan to take a sample of 10 students in my DMC100 class. Which of the following is a simple random sample.

I write the names of all students on similar slips of paper, put the slips in a box, mix well, and draw 10 slips from the box. The 10 names drawn are my sample.

Does regular church attendance lengthen people's lives? One study of the effect of regular attendance at religious service gathered data from a random sample of 3617 adults. The researchers measured whether a person attended religious services regularly and length of life. Which of the following is true?

In this study, regular attendance of religious services is the explanatory variable and length of life is the response variable

Chipotle Mexican Grill, an American chain of fast casual restaurants, is considering marketing shrimp as a new protein option, for their burrito bowls. They will be using food taste testers to collect data and decide whether shrimp should be introduced. A variety of shrimp flavors are being tested (steamed, grilled, lime-cilantro, and Old Bay ® ). Taste testers will rate their enjoyment of each flavor profile using a 1 to 5 Likert Scale (1- Gross! to 5- Delicious!). What is the control?

Steamed (no flavor)

A university is investigating the difference between career goals of male and female students attending the school. From all the male students, they randomly select 500 students to complete a survey, and from all the female students, they randomly select another 500 students to complete the same survey. Identify the sampling method described.

Stratified sample

The Denver Police Department wants to know if Hispanic residents of Denver believe that the police use racial profiling when making traffic stops. A sociologist prepares several questions about the police. The police department chooses an SRS of 200 mailing addresses in predominantly Hispanic neighborhoods and sends a uniformed Hispanic police officer to each address to ask the questions of an adult living there. The sample is

The Hispanic residents who respond to the survey

Select the true statement.

The ability of an observational study to uncover causal relationships is more limited than that of an experimental study.

Which of the following best describes the following poll question? "Please indicate how much you agree or disagree with the following statement: I feel that the staff and faculty at Goucher are accessible. Provide an answer between 1 to 5, with 1 meaning strongly disagree, and 5 meaning strongly agree.

This question should be broken up into two statements, one about the staff and one about the faculty.

A Goucher Professor wants to conduct a study to determine if listening to music while studying produces better test results in college students. She uses a computer to generate a random list of students from the entire student population, and then performs a controlled study where one randomly selected group of students is not allowed to listen to music while studying and one randomly selected group listens to music while studying for each exam. The groups are carefully monitored and the differences in grades are recorded. Which of the following best describes this scenario as to why this data is not trustworthy?

This survey is an example of convenience sampling.

A researcher wants to conduct a study to find the proportion of pet owners that vaccinate their pets. She asks simple random sample of pet owners the following: "Should concerned dog owners vaccinate their pets?" True or False: This survey question is an example of a leading question, which is a type of response bias.

True

Baltimore Bike Share1 is a city run bicycle rental program. Bicycle kiosks are placed throughout the city. For a single ride, bikes may be rented for $2. Bikes may be returned to any kiosk. All bikes are equipped with a GPS device so that the users and the Maryland Department of Transportation (MDOT) may track behavior. A MDOT researcher would like to know more about the behavior of the riders. She would like to investigate gender differences in riders. When riders register, they include age, gender and other demographic information. True or false: this is a census.

True

Select each of the following that describe a statistically significant effect.

Unlikely to be explained by mere chance. good evidence of an effect that researchers were searching for.

What are the effects of repeated exposure to an advertising message? The answer may depend on both the length f the ad and how often it is repeated. An experiment investigated this question using undergraduate students. All students viewed a 40 minute television program that included ads for a new smartphone. Some subjects saw a 30 second commercial; others a 90-second commercial. The same commercial was shown either one, three, or five times during the program. After viewing, all the students answered questions about their recall of the ad, their attitude toward the smartphone, and their intention to purchase it. In this experiment, the length of the commercial and the number of times it was shown are

the explanatory variables.

What are the effects of repeated exposure to an advertising message? The answer may depend on both the length of an ad and how often it is repeated. An experiment investigated this question using undergraduate students. All students viewed a 40-minute television program that included ads for a new smartphone. Some subjects saw a 30-second commercial. The same commercial was shown either one, three, or five times during the program. After viewing, all the students answered questions about their recall of the ad, their attitude towards the smartphone, and their intention to purchase it. In this experiment, the length of the commercial and the number of times it was shown are...

the explanatory variables.

Why should a researcher account for lurking variables in an experiment?

to isolate the effect of the explanatory variables on the response variables

Why does a researcher control for variables in an experiment?

to uncover causal relationships between variables

True or False: Taking a convenience sample may lead to undercoverage of the population.

true

True or false: "Statistically significant" basically means "due to more than random chance."

true

To reduce bias, one needs to:

use random sampling