6th Grade Math Textbook, Fundamentals

 &KDSWHU

8-1

In a , each member or part of the

population or total group has an equally likely

chance of being chosen.

Example: every third person walking along a

main thoroughfare

random sample In a , members of a

population or total group are chosen

because they are readily available.

Example: all 20 people standing at a

bus stop

convenience sample

A random sample is more likely to fairly represent a population than a

convenience sample. So for Alonzo to gather the most useful information

about what voters think of bicycle lanes, he should survey a random sample

of that population.

Samples may or may not be representative of a population. If a sample of

a population is carefully chosen, it shares that population’s characteristics.

If the sample is notrepresentative of a population, the conclusions drawn

from it may be erroneous.

Erroneous results may derive from a bias in the survey or a flaw in the

sampling procedure. A is anything that favors a particular outcome.

Examples of bias can include the way a question is asked or the way a

sample is chosen. A biased sample will not be representative of the

population under study.

Alonzo’s results would be biased if he surveyed only people shopping in a

bicycle store. The results would also be biased if he asked a registered voter

a question such as, “What would you think of devoting space to bicycle lanes

on our already crowded and narrow city streets?”

bias

Samples and Surveys

Objective To use sampling to conduct a survey• To make and use cumulative frequency tables

to organize data• To use a sample to predict data for an entire population

Alonzo works for a city planner. He wants to find out what
the city’s voters think of the mayor’s plan to put bicycle lanes
on most streets. Since it is impractical to question every citizen,
how can Alonzo gather this information?

To gather information about the opinions of a large group

of people, Alonzo can conduct a survey of a sample of that

population.

A is an examination of public opinion, attitudes, or

behavior. Alonzo’s survey will consist of finding out what

people think about having bicycle lanes on most streets.

A is a group of people or things. The population

for Alonzo’s survey is all city residents who are registered

voters. Questioning each voter would be impractical, so Alonzo

needs to question a part of that larger population, called a

. A sample is said to be a if it has
characteristics similar to the entire population.

Two kinds of samples are random samplesand convenience samples.

sample representative sample

population

survey