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census

the collection of data from every member of a population

representative sample

a sample in which the relevant characteristics of the sample members are generally the same as the characteristics of the population

bias

design or conduct tends to favor certain results

random sample

one in which every member of the pop has an equal chance of being selected to be part of the sample

simple random sampling

every possible sample of a particular size has an equal chance of being selected

systematic sampling

using a system such as choosing every 50th member of the population

convenience sampling

we use a sample that happens to be convenient to select

cluster sampling

first divide pop into groups, or clusters, and select some of these clusters at random. then obtain the sample by choosing all the members within each of the selected clusters

stratified sampling

use this method when concerned about the differences among subgroups, or strata, within a population. first identify the strata, then draw a random sample within each stratum. total sample consists of all samples from individual strata