Sample Surveys Study Guide (page 4)

Updated on Oct 5, 2011


In each question, identify whether the sample is a stratified random sample or a cluster sample.

  1. A large school system decided to survey sophomores within its high schools. Three schools were randomly selected, and all sophomores in those schools were included in the sample.
  2. A professional society wants to improve its member services. It takes a simple random sample of current members and another simple random sample of members who have chosen not to renew. All people selected are surveyed.


  1. This sampling plan leads to a cluster sample. The schools are the clusters, which are randomly selected. The sophomores within each school are the cluster members.
  2. This sampling plan results in a stratified sample. There are two strata: current members and members who have not renewed their membership. A simple random sample is selected within each stratum.

Sample Surveys In Short

Sample surveys are very useful for estimating the proportion of population units with a specific trait or opinion. Selecting a sample that allows us to make unbiased estimates of this proportion is challenging. Simple random sampling is appealing and leads to simple estimates, but selecting a true simple random sample may be physically impossible. For large surveys, stratified random samples, cluster samples, systematic samples, or a combination of these in a multistage sample may be easier to implement, more cost effective, and produce good estimates. Random-digit dialing approximates a simple random sample of all households with telephones in the region of interest.

Find practice problems and solutions for these concepts at Sample Surveys Practice Exercises.

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