The research glossary defines terms used in conducting social science and policy research, for example those describing methods, measurements, statistical procedures, and other aspects of research; the child care glossary defines terms used to describe aspects of child care and early education practice and policy.
A random sample of a population, which ensures that each member of the population has a chance of being selected for the sample.
A probit model is a type of regression where the dependent variable can only have two values. For example, a child from a low income family is either enrolled in a Head Start program or not.
Product Moment Correlation Coefficient
See Pearson's Correlation Coefficient.
Research that is conducted in order to determine the effectiveness of an intervention program.
Estimates of the future size and other demographic characteristics of a population, based on an assessment of past trends and assumptions about the future course of demographic behavior.
Propensity Score Matching
Propensity score matching is a statistical matching technique that is used to estimate the effect of a treatment or intervention when data come from a nonrandomized (observational) design. It uses a set of observable characteristics to predict the probability that participants will be assigned the treatment. Its purpose is to eliminate or reduce systematic differences between those who received the treatment and those who did not; thus, mimicking a randomized controlled trial design.
A variable used to "stand in" for another variable. Proxy variables are used when the variable of interest is not available in the data, either because it was not collected in the data or because it was too difficult to measure in a survey or interview.
There are two important psychometric properties of any test or measure: reliability and validity. Reliability refers to the consistency of a measure and validity refers to the accuracy of the measure. (See definitions of reliability and validity elsewhere in the glossary.)
A sampling strategy in which the researcher selects participants who are considered to be typical of the wider population. Since the sample is not randomly selected, the degree to which they actually represent the population being studied is unknown.