Population vs Samples

Population:
All of the individuals in the group being studied. For example; all of dogs in shelter

Sample:
All of the mixed breed dogs in animal shelter

3 types of Samples:

Convenience Sample
A sample created by choosing individuals from the population who are EASY TO ACCESS.

Voluntary Response Sample
A sample created by INVITING the whole population to participate.

Random Sample
A sample created by choosing a specific number of individuals RANDOMLY from the whole population. You can use the Random Sample to make predictions about the population.

2 types of Random Sample:

Stratified Sample
Dividing the whole population into distinct groups, then choosing the same fraction of members from each group

Systematic Sample
Choosing individuals at fixed intervals from an ordered list of the whole population.