AP stats samples

Simple random sample (SRS)

N individuals from pop. Chosen in a way that everybody has equal chance of being selected and every group of N individuals has an equal chance of being chosen.

SRS advantages and disadvantages

A-unbiased, easy

D-large variance, may not be representative, must have sampling frame (list of population)

Stratified random sample

Population is divided into strata (homogeneous groups (groups that are alike based upon some characteristics of group members)) and SRS’s are pulled from each stratum

Stratified Advantages and Disadvantages

A- more precise and unbiased than SRS, less variability, less expensive if strata already exists

D-hard to do if you have to decide stratum, formulas for SD and confidence are more complicated, needs sampling frame

Cluster Sample

Based upon location, randomly pick a location and sample all there

Cluster Advantages and Disadvantages

A-unbiased, cost is reduced, sampling frame may not be available (not needed) ⭐️

D-clusters may not be representative of population, formulas are complicated

Multistage sample

-select successively smaller groups within the population in stages, SRS used at each stage