4.1 CLUSTERS AND CLUSTER SAMPLESBy Keaton Kemnitz

&

Esteban Luis Asencio Otero Garcia de Guantanemo Masson

CLUSTERS

When a population is divided into smaller groups, or clusters, that mirror the characteristics of the population

CLUSTER SAMPLE

To make a cluster sample, divide the population into clusters.

Then choose an SRS, or stratified random sample, of the clusters.

All individuals in the chosen clusters are included in the sample.

4.1: WHAT NOT TO DO IN A SURVEY

BIAS

Failure to use random sampling often results in bias Bias are systematic errors in the way a sample

represents the population The design of a statistical study shows bias if it

systematically favors certain outcomes

VOLUNTARY RESPONSE SAMPLE

A voluntary response sample consists of people who choose themselves by responding to a general appeal. Voluntary response samples show bias because people with strong opinions (often in the same direction) are most likely to respond

CONVENIENCE SAMPLE

Choosing individuals who are easiest to reach results in a convenience sample

Convenience samples are prone to large bias due to this fact