Algebra II. Members are chosen using a method that gives everyone an equally likely chance of being selected. Simple Random Sample.

Sampling Methods

Algebra II

Members are chosen

using a method that gives everyone an equally likely chance of being selected.

Simple Random Sample

Members are chosen

using a pattern

Systematic Sample

The population is first

divided into groups. Then member are randomly chosen from each group.

Stratified Sample

Divide the population

into logical groups, then select ALL of the members of a particular group.

Cluster Sample

Members are chosen

because they are easily accessible.

Convenience Sample

Members volunteer to

participate

Self-Selected Sample

In a random sample, each

person or object has an equally likely chance of being selected. A random sample is most likely to produce a sample that is representative of a population.

Random Sample

A biased sample is a sample

that is not representative of a population. In a biased sample, the population can be underrepresented or overrepresented.

Biased Sample

One or more of the parts

of the population are left out when choosing the sample.

Underrepresented

A greater emphasis is

placed on one or more parts of a population when choosing a sample.

Overrepresented

Sampling Methods Practice

Algebra II

Directions: For each of the following, classify the type of sampling used. If there are any

under- or over-represented groups, state them.

The officials of the NFL want to know how players feel about some proposed changes to the NFL rules. They decide to ask a sample of

about 100 players.

The officials choose the first 100 players that volunteer their opinions.

Type of Sampling: Self-Selected Sample

(A)

The officials randomly choose 3 players from each of the 32 teams in the NFL.

Type of Sampling: Stratified Sample

(B)

The officials have a computer generate a list of 100 players from a database that includes all of the players in the NFL.

Type of Sampling: Simple Random Sample

(C)

Since NFL headquarters are in NYC, they choose the entire Giants team for survey.

Type of Sampling: Convenience Sample

(D)

They choose a team from the AFC and NFC and ask every player on those teams.

Type of Sampling: Cluster Sample

(E)

A town recently passed a leash law for dogs. A survey asks whether the town should designate an off-leash area where dogs can roam freely in the town park.

A survey of 100 dog owners shows that 92% say yes and 8% say no.

Type of Sampling: Cluster Sample

(A)

Survey the first 50 people walking in the park that day.

Type of Sampling: Convenience Sample

(B)

Randomly choose 100 residents of the surrounding neighborhoods.

Type of Sampling: Simple Random Sample

(C)

The manager of food services at a local high school is interested in

assessing student opinion about a new lunch menu in the school cafeteria, and plans to conduct a sample survey of the student population.

Randomly select one day of the week and then select the first 30 students who enter the cafeteria on that day.

Type of Sampling: Convenience Sample

(A)

Post the survey on the school website and use the first 30 surveys that are submitted.

Type of Sampling: Self-Selected Sample

(B)

Randomly select 30 students from a list of all students in the school.

Type of Sampling: Simple Random Sample

(C)

Randomly select one classroom in the school and then select the first 30 students who enter that classroom.

Type of Sampling: Cluster Sample

(D)

For a statistics project, a group of students decide to collect data in order to approximate the percentage of people in the town who are left-handed. They ask every third student entering the school cafeteria whether he or she is left-handed or right-handed.(a) What type of sampling did this group use?(b) What populations can they draw a conclusion

about from their data?(c) Suggest a better method that would allow

students to draw a conclusion about all the residents in their town.

Final Question!

(a) Systematic Sample (b) Students at a particular school,

presumably in a particular age range, who eat lunch during a particular shift.

(c) Answers may vary, but should be a form of random sample.

Final Question: Answers