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AP Statistics Name____________ Key _________________

1.  Identify (as precisely as possible) the population and the sample if an insurance company wants

to monitor the quality of its procedures for handling loss claims from its auto insurance

policyholders. Each month the company selects an SRS of 50 claims filed that month to

examine them for accuracy and promptness.

Population – all of the claims filed for that month

Sample – the 50 claims that were examined

2.  A local radio talk-show host asks viewers to call in and vote for or against a proposed plan to

raise the prices charged by municipal parking meters in a downtown shopping district. 75% of

the respondents are opposed to the increase. Describe one possible source of error or bias

that might arise in this poll and indicate the direction in which the estimate might be biased.

What is the name for this kind of bias?

This is a voluntary sampling which causes Selection Bias. The people most likely to call in arethose who would be affected and they probably would not want to raise the prices so this

percentage is higher than expected.

3.  Two different organizations conduct polls in a city whose mayor has been accused of taking

bribes. One poll asks a SRS of city residents, “Do you think the mayor should resign because

of accusations of his criminal activity?” The other asks, “Do you think the mayor should

resign?” The first poll concluded that the majority of city residents think the mayor should

resign. The second poll drew exactly the opposite conclusion. Explain why their results might

be so different. What type of bias is this?

This is Response Bias since the question is worded so that the subjects are led to answer that

they want the mayor to resign.

4.  Your school will send a delegation of 35 seniors to a student life convention. 200 girls and 150

boys are eligible to be chosen. If a sample of 20 girls and a separate sample of 15 boys are

each selected randomly, it gives each senior the same chance to be chosen to attend the

convention.

a.  Is it a SRS? Explain

This is not a SRS since all groups of 35 do not have the same chance of being chosen. There

would never be a group of 35 girls.

b.  Beginning at line 108 in the random digits table, reproduced below, select the first three

senior girls to be in the sample. Explain your procedures clearly.

179, 90, 9

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5.  The school’s newspaper has asked you to contact 100 of the approximately 1100 students at

the school to gather information about student opinions regarding food at your school’s

cafeteria.

a.  If you randomly choose 25 from each class (freshmen, sophomore, junior, senior) to

survey, what type of sampling technique is being used?

Stratified – some from all

b.  If you decided to ask the first 100 in the line at lunch, what type of sampling technique is

being used?

Convenience

c.  If you decide to randomly choose one student in each of the 100 classrooms, what type of

sampling technique is being used?

Stratified

d.  If you decide to ask every tenth student that walks in the school, what type of sampling is

being used?

Systematic

e.  If you decide to ask all of the students in four randomly chosen classrooms, what type of

sampling is being used?

Cluster – all from some