Holt CA Course 1

7-7 Selecting Samples

SDAP2.2 Identify different ways of selecting a sample (e.g., convenience sampling, responses to a survey, random sampling) and which method makes a sample more representative for a population.

California Standards

Holt CA Course 1

7-7 Selecting Samples

Vocabularysystematic sampleconvenience sampleself-selected sample

Holt CA Course 1

7-7 Selecting Samples

Recall that in a random sample each member of the population has an equal chance of being selected. Some other types of sampling methods are described below.

Sampling Methods

Method Description

systematic sample A member of the population is selected at random, and then others are selected by using a pattern.

convenience sample The most-available members of the population are chosen.

self-selected sample Members of the population volunteer to respond to a survey.

Holt CA Course 1

7-7 Selecting Samples

The manager of a company wants to know how many employees have a laptop computer at home. Identify each type of sampling method.

Additional Example 1: Identifying Sampling Methods

A. The manager randomly chooses 40 names from a list of all employees.

This is a random sample because every employee has an equal chance of being selected.

B. The manager surveys the first 50 employees as they arrive at the office.

This is a convenience sample because the group of employees is easy to reach.

C. The manager places a stack of survey forms in the company cafeteria.

This is a self-selected sample because the group of employees chooses whether to complete the surveys.

Holt CA Course 1

7-7 Selecting Samples

You want to know how often students in high school take tests. Identify each type of sampling method.

Check It Out! Example 1

A. You survey the first 50 students as they arrive at school.

This is a convenience sample because the group of students is easy to reach.

B. You place a stack of survey forms in the student library.

This is a self-selected sample because the group of students chooses whether to complete the surveys.

C. You randomly choose 40 names from a list of all students and then every 5th name after that.

This is a systematic sample because the students are chosen at random and then the other names are chosen by using a pattern.

Holt CA Course 1

7-7 Selecting Samples

Random samples and systematic samples are more likely to be representative of a population than either convenience samples or self-selected samples.

Holt CA Course 1

7-7 Selecting Samples

Determine which sampling method will better represent the entire population. Justify your answer.

Additional Example 2: Analyzing Sampling Methods

Jon’s sample is a random sample, giving every band member an equal chance to be surveyed, so it is the better method.

Band Uniform StyleSampling Method Results

Maria surveys only the band students she knows personally.

84% want blue uniforms

Jon writes each band student’s name on a card. He questions those students whose name he draws.

61% want blue uniforms

Holt CA Course 1

7-7 Selecting Samples

Determine which sampling method will better represent the entire population. Justify your answer.

Check It Out! Example 2

Ferdinand’s method produces results that better represent the entire swimming team population.

Swimming SchedulingSampling Method Results

Ferdinand surveys every other swimmer on the team.

72% want practice early

Anna-Maria questions the swimmers who are in her Biology class.

50% want practice early