ap stats

What is the population

• The population in a statistical study is the
• entire group of individuals we want
• information about.The population in a statistical study is the
• entire group of individuals we want
• information about.

What is a census

• A census collects data from every
• individual in the population.

simple random sampling

systematic

Slide 5

What is a sample

• A sample is a subset of individuals in the
• population from which we collect data.

What is a convenience sample

• Convenience sampling selects
• individuals from the population who
• are easy to reach (from the perspective
• of the researcher).

Stratified Random Sampling (SRS)

• One of the most common alternatives to
• SRS is called stratified random sampling.
• This method involves dividing the
• population into non-overlapping groups
• (strata) of individuals who are expected to
• have similar responses, sampling from
• each of these groups, and combining
• these “subsamples” to form the overall
• sample.

strata

• Strata are groups of individuals in a
• population who share characteristics
• thought to be associated with the
• variables being measured in the study.

Stratified Random Sampling (SRS)

• Stratified random sampling selects a
• sample by choosing an SRS from each
• stratum and combining the SRSs into
• one overall sample. This works best when the individuals
• within each stratum are similar
• (homogeneous) with respect to what is
• being measured and when there are large
• differences between strata.

cluster samples

• A cluster is a group of individuals in the
• population that are located near each
• other.
• Cluster sampling selects a sample by
• randomly choosing clusters and
• including each member of the selected
• clusters in the sample.Cluster sampling is used for practical
• reasons as it often saves time and/or
• money.
• The individuals within each cluster
• should be heterogenous (mirroring the
• population), and clusters should be
• similar to each other in their
• composition.
• Each cluster is like a mini-population.