Question 1

Define a simple random sample.

Accepted Answer

A simple random sample is one in which every group of same size from the population has an equally likely chance of being chosen.

Question 2

A high school principal wishes to determine what proportion of the school's students likes the new school mascot. The principal decides to survey every 25th name from the school enrollment records (an alphabetical list of all students at the school). Is this a valid simple random sampling technique? Why or why not?

Accepted Answer

Taking every 25th name from an alphabetical listing of students is not a valid simple random sampling technique since no two students who follow one another on the list could ever be part of the sample. This contradicts the idea that in a simple random sample, every collection of individuals has an equal chance of being chosen.

Question 3

In order to determine what proportion of a town's residents approves of a new plan for trash collection, the town council placed an ad in the newspaper asking residents to phone in their opinions. Explain why the results of this poll may differ from the actual beliefs of all residents in the town.

Accepted Answer

The sampling technique described uses self-selection. Only those residents with extreme views on the new plan are likely to respond to the advertisement. A second problem with the poll technique described is that not all residents who will be affected by the new trash collection plan are likely to read the newspaper. The opinions of a large number of residents are therefore unlikely to be included in the results of the poll.

Question 4

A school principal is concerned with the increasing level of absenteeism in the school. A meeting of parents, teachers, and students is called at which the principal expresses her concern and describes an experimental program that will be instituted to try to curb absenteeism. After two months, absenteeism is down by 15%. Explain how confounding variables may have affected the results of the experiment.

Accepted Answer

The answer of A school principal is concerned with the...

Question 5

In order to determine if students on a college campus are in favor of a tuition hike to pay for expanded parking services, a member of the student senate surveys 25 people in a commuter parking lot. Why is this a poor sampling technique?

Accepted Answer

The answer of In order to determine if students on...

Question 6

One July, the city council of a small town decides to impose an experimental curfew on all residents younger than 18 years to cut down on loitering in the town square. After four months, the number of teens found in the square after dark has decreased by 80%, and the council declares the curfew a success. Explain why this conclusion may not be valid.

Accepted Answer

The answer of One July, the city council of a...

Question 7

We must use a random digits table to choose a sample of eight names from the roster of a club with 100 members. Why can we use two-digit numbers from the table to select our sample?

Accepted Answer

The answer of We must use a random digits table...

Question 8

What is the difference between an observational study and an experiment?

Accepted Answer

The answer of What is the difference between an observational...

Question 9

Explain the difference between bias and variability in sampling results.

Accepted Answer

The answer of Explain the difference between bias and variability...

Question 10

A biologist draws a sample of 200 fish from a lake to test for mercury levels. She finds that 8% have levels above the limits set as healthy. Describe the population for this study.

Accepted Answer

The answer of A biologist draws a sample of 200...

Question 11

Convenience samples are said to be highly likely to produce bias in survey results. Explain why this is true.

Accepted Answer

The answer of Convenience samples are said to be highly...

Question 12

A farmer believes that exposing chickens to classical music will cause them to produce more eggs. Describe how the farmer may design a randomized comparative experiment to test this theory.

Accepted Answer

The answer of A farmer believes that exposing chickens to...

Question 13

A polling company working for a candidate for governor surveys a sample of 2500 registered voters in the state to determine if they are in agreement with the candidate's stand on gun control. Describe the population for this study.

Accepted Answer

The answer of A polling company working for a candidate...

Question 14

In a poll of 2500 residents of a state, it is found that 480 are in favor of naming the grasshopper the state insect. What is the sample proportion for this poll?

Accepted Answer

The answer of In a poll of 2500 residents of...

Question 15

Why do opinion polls usually report a margin of error with the results of a survey? What does the margin of error mean?

Accepted Answer

The answer of Why do opinion polls usually report a...

Question 16

We wish to know what proportion of students at a major university believes too much emphasis is placed on athletics at the school. Explain how we could choose a sample of 500 students to reduce the possibility of bias in the results.

Accepted Answer

The answer of We wish to know what proportion of...

Question 17

The marketing department of a large national corporation wishes to determine what proportion of the residents of a state may be interested in buying its new product. Describe how the corporation might use a multistage random sampling process to choose a sample of the state's residents to survey.

Accepted Answer

The answer of The marketing department of a large national...

Question 18

A school superintendent believes a new approach to teaching children to read will produce better standardized test scores in the district. Describe how the superintendent may design a randomized comparative experiment to test this theory.

Accepted Answer

The answer of A school superintendent believes a new approach...

Question 19

Can we eliminate variability in results of sampling? Why or why not?

Accepted Answer

The answer of Can we eliminate variability in results of...

Question 20

A marketing department surveys 1500 shoppers and finds that 950 would visit a new store more often if it was open on Sunday evenings. What is the sample proportion in this survey?

Accepted Answer

The answer of A marketing department surveys 1500 shoppers and...

Quiz 7: Data for Decisions