2.3 Sampling TechniquesTerms

Population: refers to all individuals who belong to a group being studied

2.3 Sampling TechniquesTerms

Population: refers to all individuals who belong to a group being studied

Sample: a group or items selected from the population

Example 1 Identify the Population in each survey question below

How many scars did monkeys get who live in Africa that is dominated by lions?

Example 1 Identify the Population in each survey question below

How many scars did monkeys get who live in Africa that is dominated by lions?Population -> monkeys in Africa

Example 1 Identify the Population in each survey question below

How many scars did monkeys get who live in Africa that is dominated by lions?Population -> monkeys in Africa

Do students prefer robot teachers or human teachers? This is real debate with regards to teachers of English in Asia.

Example 1 Identify the Population in each survey question below

How many scars did monkeys get who live in Africa that is dominated by lions?Population -> monkeys in Africa

Do students prefer robot teachers or human teachers? This is real debate with regards to teachers of English in Asia.Population -> students

More terms Sampling frame: the group actually

have a chance of being selected

More terms Sampling frame: the group actually

have a chance of being selected

Simple random sample: a sample in which every member of the population has an equal and independent chance of being selected

More terms Systematic sample: a sample selected

by listing a population sequentially and choosing members at regular intervals

interval = population size / sample size

Systematic sample example

interval = pop. of 100/ sample of 20 = every 5th person surveyed

Stratified sample: a sample in which each group is represented in the same proportion as it appears in the population

Stratified sample: a sample in which each group is represented in the same proportion as it appears in the population

i.e., Survey TPS students if they like the i-Phone. Note that there are more gr. 12s than gr. 8s so they should represent more of the survey.

Method Stratified sample:

So you choose to survey a fraction of each group within the sample to ensure each group is represented.

Method Stratified sample:

Choose a fraction with justification, say 30%.

Grade# of

StudentsRel.

FrequencyNumber

Surveyed8 12 0.059 32 0.1310 47 0.1911 69 0.2912 78 0.33Total 238 1

More terms Stratified sample:

Choose a fraction with justification, say 30%.

Grade# of

StudentsRel.

FrequencyNumber

Surveyed8 12 0.05 3

9 32 0.13 9

10 47 0.19 14

11 69 0.29 20

12 78 0.33 23

Total 238 1 69

More Sample Types

Cluster sample - the total population is divided into groups (or clusters) and a simple random sample of the groups is selected.

Cluster sample - the total population is divided into groups (or clusters) and a simple random sample of the groups is selected.

Example:

a fast-food chain could save time and money by surveying all its employees at randomly selected locations

instead of surveying randomly selected employees throughout the chain

Cluster sample - the total population is divided into groups (or clusters) and a simple random sample of the groups is selected.

Multi-stage sample – several levels of ran. Sampling

Cluster sample - the total population is divided into groups (or clusters) and a simple random sample of the groups is selected.

Multi-stage sample – several levels of ran. Sampling

Example: To examine Ontario households, you can randomly survey certain cities, then randomly survey random blocks, and then survey random houses.

Sample Types Cluster sample - the total population is

divided into groups (or clusters) and a simple random sample of the groups is selected.

Multi-stage sample – several levels of ran. sampling

Voluntary-response sample – researcher invites any member of population into survey

Cluster sample - the total population is divided into groups (or clusters) and a simple random sample of the groups is selected.

Multi-stage sample – several levels of ran. sampling

Voluntary-response sample – researcher invites any member of population into survey

Convenience sample - sample selected but it’s easily accessible

In class / Home work:1) Homework: Pg. 117 #1, 2, 3, 6, 8, and 9 *check your work with answers in the back – pg 618

2) Quiz on Friday – histogram/bar graph, definitions, sample types