
Population
The aggregate of all the elements, sharing some common set of characteristics, that compromises the universe for the purpose of the marketing research problem.

Census
A complete enumeration of the elements of a population or study objects.

Sample
A subgroup of the elements of the population selected for participation in the study.

Target Population
The collection of elements or objects that possess the information sought by the researcher and about which inferences are to be made.

Element
An object that possesses the information sought by the researcher.

Sampling Unit
The basic unit containing the elements of the population to be sampled.

Sampling Frame
A representation of the elements of the target population. It consists of a list or set of directions for identifying the target population.

Bayesian Approach
A selection method in which the elements are selected sequentially. The Bayesian approach explicitly incorporates prior information about population parameters as well as the costs and probabilities associated with making wrong decisions.

Sampling with Replacement
A sampling technique in which an element can be included in the sample more than once.

Sampling without replacement
A sampling technique in which an element cannot be included in the sample more than once.

Sample Size
the number of elements to be included in a study.

Nonprobability Sampling
Sampling techniques that do not use chance selection procedures. Rather, they rely on the personal judgment of the researcher.

Probability Sampling
A sampling procedure in which each element of the population has a fixed probabilistic chance of being selected for the sample.

Convenience Sampling
A nonprobability sampling technique that attempts to obtain a sample of convenient elements. The selection of sampling units is left primarily to the interviewer.

Judgmental Sampling
A form of convenience sampling in which the population elements are purposely selected based on the judgment of the researcher.

Quota Sampling
A nonprobability sampling technique that is twostage restricted judgmental sampling. The first stage consists of developing control categories or quotas of population elements. In the second stage, sample elements are selected based on convenience or judgment.

Snowball Sampling
A nonprobbility sampling technique in which an initial group of respondents is selected randomly. Subsequent respondents are selected based on referrals or information provided by the initial respondent. This process may be carried out in waves by obtaining referrals from referrals.

Simple Random Sampling
A probability sampling technique in which each elements in the population has a known and equal probability of selection. Every element is selected independently of every other element and the sample is drawn by a random procedure form a sampling frame.

Systematic Sampling
A probability sampling technique in which the sample is chosen by selecting a random starting point and then picking every i^{th }element in succession from the sampling frame.

Stratified Sampling
A probability sampling technique that uses a twostep process to partition the population into subpopulations, or strata. Elements are selected from each stratum by a random procedure.

Cluster Sampling
First, the target population is divided into mutually exclusive and collectively exhaustive subpopulations called clusters. Then a random sample of clusters is selected based on a probability sampling technique such as simple random sampling. For each selected cluster, either all the elements are included in the sample or a sample of elements is drawn probabilistically.

Area Sampling
A common form of cluster sampling in which the cluster consists of geographic areas such as counties, housing tracts, blocks or other area descriptions.

Probability proportionate to Size Sampling
A selection method in which the clusters are selected with probability proportional to size and the probability of selecting a sampling unit in a selected cluster varies inversely with the size of the cluster.

Sequential Sampling
A probability sampling technique in which the population elements are sampled sequentially, data collection and analysis are done at each stage, and a decision is made as to whether additional population elements should be sampled.

Double Sampling
A sampling technique in which certain population elements are sampled twice.

