sample
a subset of elements from the larger population
population
the entire set of elements ( individuals, cities, states, prisons, schools) in which we are interested
cross-population generalizability
exists when findings about one group, population, or setting hold true for other groups, populations, or settings. This is also called external validity
sample generalizability
exists when a conclusion based on a sample, or subset, of a larger population holds true for that population
representative sample
a sample that looks like the population from which it was selected in all respects that are potentially relevant to the study. The distribution of characteristics among the elements of a representative sample is the same as the distribution of those chara
probability of selection
the likelihood that an element will be selected from the population for inclusion in the sample
random selection
the fundamental element of probability samples. The essential characteristics of random selection is that every element of the population has a known and independent chance of being selected into the sample
sampling frame
a list of all elements or other units containing the elements in a population
sampling error
any difference between the characteristics of the population from which it was drawn. The larger the sampling error, the less representative the sample is of the population
probability sampling
sampling methods that allow us to know in advance how likely it is that any element will be selected from the population for inclusion in the sample.
simple random sampling
a method of sampling in which every sample element is selected only on the basis of change, through a random process
systematic sampling
a method of sampling in which sample elements are selected from a list of from sequential files, with every nth element being selected after the first element is selected randomly within the first interval
stratified random sampling
a method of sampling in which sample elements are selected separately from population strata that are identified in advance by the researcher
cluster sampling
a sampling method in which elements are selected in two or more stages, with the first stage being the random selection of naturally occurring clusters and the last stage being the random selection of elements within clusters
nonprobability sampling
sampling method in which the probability of selection of population elements unknown
availability sampling
sampling in which elements are selected on the basis of convenience
purposive sampling
a nonprobability sampling method in which elements are selected for a purpose, usually because of their unique position
quota sampling
a nonprobability sampling method in which elements are selected to ensure that the sample represents certain characteristics in proportion to their prevalence in the population
snowball sampling
members of your sample recruit others from their network for your study