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Statistics Chapter 10: Sample Surveys
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You are trying to study the amount of financial aid students at your University receive. You sample 50 students and find out the average size of their financial aid packages. The average of your sample is a __________.
sample statistic.
You are doing a study for a non-profit group helping at-risk children in your city. Suppose you know that 14.2% of the children in your city live in poverty. This percentage is an example of a __________.
population parameter
If you create an online survey, individuals can choose on their own whether to participate in the sample. This causes a form of bias called __________.
voluntary response
When you sample so that every combination of individuals in your population has an equal chance of being chosen you are taking a __________.
simple random sample (srs)
A friend of yours in your intro stats class obtains permission to randomly sample the University student body to conduct a satisfaction survey on some recent changes to the enrollment process. She randomly samples 50 freshmen, 50 sophomores, 50 juniors, and 50 seniors. This is an example of a __________ sample.
stratified
Some friends of yours in a political science class are angry about a new town ordinance restricting off-campus parties. They make an online survey asking students' opinions. This type of sampling might be classified as a __________ sample.
convenience
At its website, a polling company publishes results of a new survey each day. Scroll down to the end of the published results and you'll find a statement that includes words as shown below.
Results are based on telephone interviews with 1,008 national adults, aged 18 and older, conducted on April 2-5, 2007 ... In addition to sampling error, question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of public opinion polls.
a. Identify the population of interest.
b. What is the sampling frame?
c. What problems, if any, would you be concerned about in matching the sampling frame with the population?
a. Everyone in the nation that is 18+
b. Everyone with a telephone
c. Some people do not have telephones
Researchers want to estimate the percentage of people who thought drinking and driving was a serious problem. Researchers waited outside a bar to question people. They usually find 17 % of bar patrons believe drinking and driving is a serious problem.
a. Identify the Population
b. Identify the population parameter of interest
c. Identify the sampling frame
d. Identify the sample
e.Identify the sampling method
f. Identify who was left out of the study
g. Identify any potential sources of bias
a. adults
b. proportion of adults who think drinking and driving is a serious problem
c. bar patron
d. adults leaving the bar
e. cluster sample of location
f. people who do not go to that bar
g. Undercoverage bias is possible. Since those interviewed just left a bar, their opinions about drunk driving may differ from the population in general.
General Motors wants to administer a satisfaction survey to its current customers. Using their customer database, the company randomly selects 60 customers and asks them about their level of satisfaction with the company.
What type of sampling is used?
simple random
To determine her power usage, Jean divides up her day into three parts: morning, afternoon, and evening. She then measures her power usage at 2 randomly selected times during each part of the day.
What type of sampling is used?
stratified
To estimate the percentage of defects in a recent manufacturing batch, a quality control manager at Ford selects every 12th truck that comes off the assembly line starting with the fourth until she obtains a sample of 140 trucks.
Which type of sampling is used?
systematic
To determine customer opinion of their safety safety features, Toyota randomly selects 130 dealerships during a certain week and surveys all customers visiting the dealership.
Which type of sampling is used?
cluster
A group of people are classified according to music preference and then random samples of people from each group are taken.
Choose the correct sampling technique below.
Stratified sampling
A state is divided into regions using area codes. A random sample of 25 area code areas is selected.
Choose the correct sampling technique below.
Cluster sampling
The first 20 students leaving the cafeteria are asked how much money they spent on textbooks for the semester.
convenience sampling
Golf balls in a basket are shaken and then balls are selected from the basket.
random sampling
At its website, a polling company publishes results of a new survey each day. Scroll down to the end of the published results and you'll find a statement that includes words as shown below.
Results are based on telephone interviews with 1,008 national adults, aged 18 and older, conducted on April 2-5, 2007 ... In addition to sampling error, question wording and practical difficulties in conducting surveys can introduce error or bias into the findings of public opinion polls.
a. For this survey, identify the population of interest.
b.The company performs its surveys by phoning numbers generated at random by a computer program. What is the sampling frame?
c.What problems, if any, would you be concerned about in matching the sampling frame with the population?
a. everyone in the nation that is 18+
b. everyone with a telephone
c. Some people do not have telephones.
An amusement park has opened a new roller coaster. It is so popular that people are waiting for up to 3 hours for a 2-minute ride. Concerned about how patrons (who paid a large amount to enter the park and ride on the rides) feel about this, they survey every person as soon as they exit the park.
a. What kind of sample is this?
b. What is the sampling frame?
c. Is the sample likely to be representative of the population of interest?
d. What members of the population of interest are omitted?
a. a census
b. all the patrons of the park
c. Yes, the sample is likely to be representative of everyone in the park.
d. no members of the population of interest are omitted.
Administrators at a university were interested in estimating the percentage of students who are the first in their family to go to college. The university student body has about 47,000 members.
a. Select several dormitories at random and contact everyone living in the selected dorms.
b. Using a computer-based list of registered students, contact 100 freshmen, 100 sophomores, 100 juniors, and 100 seniors selected at random from each class.
c. Using a computer-based alphabetical list of registered students, select one of the first 30 names on the list at random, and then contact the student whose name is 60 names later, and then every 60th name after that.
a. cluster sample
b. stratified sample
c. systematic sample
What problems do you see with asking the following question of students? "Are you the first member of your family to seek higher education?"
Several terms are poorly defined. The survey needs to specify the meaning of "family" for this purpose and the meaning of "higher education." The term "seek" is also poorly defined as it does not specify what qualifies as seeking more education.
Administrators at a university were interested in estimating the percentage of students who are the first in their family to go to college. The university student body has about 52,000 members. The university administration is considering a variety of ways to sample students for a survey. For each of these proposed survey designs, identify the problem.
a. Publish an advertisement inviting students to visit a website and answer questions.
b. Set up a table in the student union and ask students to stop and answer a survey.
a. voluntary response bias
b. convenience sample
In a large city school system with 26 elementary schools, the school board is considering the adoption of a new policy that would require elementary students to pass a test in order to be promoted to the next grade. The PTA wants to find out whether parents agree with this plan. Listed below are some of the ideas proposed for gathering data. For each, indicate what kind of sampling strategy is involved and what (if any) biases might result. Assume the schools are homogeneous and differ from each other.
A. Randomly select one of the elementary schools and contact the parents of every student
a. What kind of bias is most likely to result.
B. Randomly select 10 parents from each elementary school. Send them a survey, and follow up with a home visit if they do not return the survey within a week.
b. What kind of bias is likely to result?
C. Randomly select 250 parents and send them a survey, follow up with a home visit if they do not return the survey within a week.
c. What kind of bias is likely to result?
D. Ask the parents for their opinions at the next PTA meeting.
d. What kind of bias is likely to result?
A. Cluster sampling
a. Undercoverage bias could result since the parents in the sample may not be representative of all parents.
B. Stratified sampling
b. Bias could result only if the sampling strategy is not followed as described
C. Simple random sample
c. Bias could result only if the sampling strategy is not followed as described
D. Convenience sampling
d. Undercoverage bias could result since only parents involved with the PTA will be sampled
A chemistry professor who teaches a large lecture class surveys his students who attend his class about how he can make the class more interesting, hoping he can get more students to attend. What does this survey method suffer from?
Undercoverage
Which of the following statements about bias are true?
I. Bias results from random variation and will always be present.
II. Bias results from a sampling method likely to produce samples that do not represent the population.
III. Bias is usually reduced when sample size is larger.
II. Bias results from a sampling method likely to produce samples that do not represent the population.
Two members of the PTA committee have proposed the accompanying questions to ask in seeking parent's opinions. Question 1 is "Should elementary school-age children have to pass high-stakes tests in order to remain with their classmates?" and Question 2 is "Should schools and students be held accountable for meeting yearly learning goals by testing students before they advance to the next grade?" Complete parts a and b below.
The answers for these two questions will definitely differ. Question 1 will probably get many "No" answers, while Question 2 will get many "Yes" answers. This is an example of response bias.
"Do you think standardized tests are appropriate for deciding whether a student should be promoted to the next grade?
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