__Sampling__

Who?
How many? Selection? Sorted?

Information:

Gender

Age

Geographical area

SES

Source

Basis for participation

Other

Population:

All the units we would like to study

The people who are the focus of the
research

Sample:

A group of people who represent the
population

Keep
record of:

Number contacted

Number participated

Number screened out and why

Number dropped out and why

Probability
sampling:

Simple random

Systematic sampling

Stratified random

Cluster

Nonprobability
sampling:

Convenience

Purposive

Snowball

Quota

Sampling
error:

Random

Systematic

Probability
theory:

To estimate how closely sample
statistics are clustered around the true population value.

Large samples

Numerous samples

Randomness (sample with replacement)

**Randomness
is necessary in order to use powerful statistics!**