R

Random Assignment
The assignment of individuals in the pool of all potential participants to either the experimental (treatment) group or the control group in such a manner that their assignment to a group is determined entirely by chance.

Random Comparison Group Design
In this research design, the comparison group is randomly selected from the population of interest, even though the treatment group is not selected randomly.

Randomized Comparative Change Design
In the experimental design known as the randomized comparative change design a treatment and control group are randomly selected for study. Both groups are administered a pre-test. The treatment group is given the treatment, while the control group is not. Both groups are tested or measured after the treatment. The test results of the two groups are compared. The pretest allows a check on the randomization process, and allows for control of any differences found.

Randomized Comparative Post-Test Design
In the experimental design known as the randomized comparative post-test design a treatment and control group are randomly selected for study. The treatment group is given the treatment, while the control group is not. Both groups are tested or measured after the treatment. The test results of the two groups are compared.

Randomized Controlled Trial
In a randomized controlled trial, the impact of a program is determined by randomly assigning individuals to an intervention group or control group.

Random Digit Dialing
Rather than selecting names and numbers of individuals to be called, computers are used to generate random sets of seven-digit numbers, which are then called as the survey sample.

Random Sampling
A procedure for sampling from a population that gives each unit in the population a known probability of being selected into the sample.

Range
A measure of spread which gives the distance between the lowest and the highest values in a distribution; a statistic used primarily with interval-ratio variables. FOR EXAMPLE, a study may report that ages in the sample ranged from 21 to 65 years.

Ratio Measure
A level of measurement which has all the attributes of nominal, ordinal, and interval measures, and is based on a "true zero" point. As a result, the difference between two values or cases may be expressed as a ratio. FOR EXAMPLE, it may be reported that person A weighed twice as much as person B, because weight is typically measured using a ratio measure (i.e., pounds).

Recidivism
The repetition of criminal or delinquent behavior.

Regression Analysis
A method for determining the association between a dependent variable and one or more independent variables.

Regression Coefficient
An asymmetric measure of association; a statistic computed as part of a regression analysis.

Regression Discontinuity Design
In this research design, subjects are placed into treatment and control groups based on a score obtained on some variable. Those scoring higher of the assignment variable are placed into one group, while those scoring lower are placed in the other group.

Regression Effects
The tendency of subjects, who are initially selected due to extreme scores, to have subsequent scores move inward toward the mean. Also known as statistical regression/regression to the mean/regression fallacy. FOR EXAMPLE, students with the highest grades in a midterm exam are more likely to have scores closer to the mean at the final. This effect may be misinterpreted in evaluation research as being a result of the program.

Regression Fallacy
The tendency of subjects, who are initially selected due to extreme scores, to have subsequent scores move inward toward the mean. Also known as statistical regression/regression to the mean/regression effect. FOR EXAMPLE, students with the highest grades in a midterm exam are more likely to have scores closer to the mean at the final. This effect may be misinterpreted in evaluation research as being a result of the program.

Reliability
The extent to which a measurement instrument yields consistent, stable, and uniform results over repeated observations or measurements under the same conditions each time. FOR EXAMPLE, a scale is unreliable if it weighs a child three times in three minutes and gets three different weights.

Reliability Assessment
An effort required to demonstrate the repeatability of a measurement or how likely a question may be to get consistently similar results. It is different from verification (checking accuracy) or validity.

Replication
The duplication of an experiment or program.

Representative
Reflecting the characteristics or nature of the larger population to which one wants to generalize.

Representative Sample
A sample that has approximately the same distribution of characteristics as the population from which it was drawn.

Request For Proposal
An open solicitation to potential grantees or contractors inviting them to compete for money available to evaluate programs.

Research Design
A plan of what data to gather, from whom, how and when to collect the data, and how to analyze the data obtained.

Resistant Statistic
A statistic that is not much influenced by changes in a few observations.

Resources
Assets available and anticipated for operations. They include people, equipment, facilities and other things used to plan, implement, and evaluate public programs whether or not paid for directly by public funds.

Response Rate
The percentage of persons in a sample who respond to a survey.

Response Style
The tendency of a respondent to answer in a specific way regardless of how a question is asked. FOR EXAMPLE, some persons may be more likely to use extreme categories, such as "very good" or "excellent", while others may shy away from use of such extremes.

Response Variable
A variable on which information is collected and which there is an interest because of its direct policy relevance. FOR EXAMPLE, in studying policies for retraining displaced workers, employment rate might be the response variable.