S

Sample
A subset of the population. Elements are selected intentionally as a representation of the population being studied.

Sample Design
The sampling procedure used to produce any type of sample.

Sampling Distribution
The distribution of a statistic.

Sampling Error
The maximum expected difference between a probability sample value and the true value.

Sampling Frame
The complete list of the universe or population of interest in the study. FOR EXAMPLE, all persons living in a given area, or all offenders eligible for a given treatment.

Scale
An aggregate measure that assigns a value to a case based on a pattern obtained from a group of related measures.

Scientific Sample
Synonymous with Probability Sample. A group of cases selected from a population by a random process. Every member of the population has a known, nonzero probability of being selected.

Scoping
Analyzing alternative ways for conducting an evaluation. It is clarifying the validity of issues, the complexity of the assignment, the users of final reports, and the selection of team members to meet the needs of an evaluation. Scoping ends when a major go/no-go decision is made about whether to do the evaluation.

Secondary Data
Data that has been collected for another purpose, but may be reanalyzed in a subsequent study. FOR EXAMPLE, state criminal history files may be searched both to analyze prior criminal history of offenders in treatment programs and to identify subsequent recidivism. However, such data was not originally collected for such purposes.

Selection Bias
Potential biases introduced into a study by the selection of different types of people into treatment and comparison groups. As a result, the outcome differences may potentially be explained as a result of pre-existing differences between the groups, as opposed to the treatment itself.

Selection Effects
1) Selection bias is a threat to the internal validity of an evaluation when the researcher chooses non-equivalent groups for comparison. FOR EXAMPLE, when the recidivism rate of a program tested on first time offenders is compared to the recidivism rate of the general prison population.

2) Selection bias is a threat to the external validity of an evaluation if the study group is not representative of the larger population to which results are intended to be inferred. FOR EXAMPLE, a program may appear successful using a group of specially selected clients (e.g., first time offenders). However, it would not be a fair test of how this program would work on the general offender population.

Self-evaluation
The evaluation of a program by those conducting the program.

Self-Reported Data
Information that program participants generate themselves that is used to assess program processes or outcomes.

Significance Level
The probability of rejecting a set of assumptions when they are in fact true.

Simple Random Sample
A method for drawing a sample from a population such that all samples of a given size have equal probability of being drawn.

Sleeper Effect
An impact of a study that does not appear immediately, but may manifest at a later time.

Spread
General term for the extent of variation among cases.

Spuriousness
A condition in which two variables vary together, but are not in fact causally related. Both may be influenced independently by a third variable. FOR EXAMPLE, it may be found that children who eat more ice cream are less likely to be involved in delinquent behavior. Rather than concluding that "ice cream consumption" reduces "delinquent behavior," it may be found that both behaviors are a function of a third variable, "income."

Staffing
Personnel required for a program or a project.

Standard
A criterion for evaluating performance and results. It may be a quantity or quality of output to be produced, a rule of conduct to be observed, a model of operation to be adhered to, or a degree of progress toward a goal.

Standard Deviation
A measure of the spread, the square root of the variance; a statistic used with interval-ratio variables.

Standard Instruments
An assessment, inventory, questionnaire, or interview that has been tested with a large number of individuals and is designed to be administered to program participants in a consistent manner. Results of tests with program participants can be compared to reported results of the tests used with other populations.

Standardized Question
A question that is designed to be asked or read and interpreted in the same way regardless of the number and variety of interviewers and respondents.

Statistic
A number computed from data on one or more variables.

Statistical Analysis
Analyzing collected data for the purposes of summarizing information to make it more usable and/or making generalizations about a population based on a sample drawn from that population.

Statistical Conclusion Validity
The extent to which the observed statistical significance (or the lack of statistical significance) of the covariation between two or more variables is based on a valid statistical test of that covariation.

Statistical Control
A statistical technique used to eliminate variance in dependent variables caused by extraneous sources. In evaluation research, statistical controls are often used to control for possible variation due to selection bias by adjusting data for program and control group on relevant characteristics.

Statistical Procedure
A set of standards and rules based in statistical theory by which one can describe and evaluate what has occurred.

Statistical Sample
Synonymous with probability sample; a group of cases selected from a population by a random process in which every member of the population has a known, nonzero probability of being selected.

Statistical Significance
The degree to which a value is greater or smaller than would be expected by chance. Typically, a relationship is considered statistically significant when the probability of obtaining that result by chance is less than 5% if there were, in fact, no relationship in the population.

Statistical Test
Type of statistical procedure that is applied to data to determine whether the results are statistically significant (that is, the outcome is not likely to have resulted by chance alone).

Statistical Weighting
A technique used to assure representation of certain groups in the sample. Data for underrepresented cases are weighted to compensate for their small numbers, making the sample a better representation of the underlying population.

Stem
The statement portion of a question.

Stem-and-Leaf Plot
A graphic or numerical display of the distribution of a variable.

Strategic Evaluation
An evaluation used by managers as an aid to decide which strategy a program should adopt in order to accomplish its goals and objectives at a minimum cost. In addition, strategy evaluation might include alternative specifications of the program design itself, detailing milestone and flow networks, manpower specifications, progress objectives, and budget allocations.

Strategic Plan
The process of comprehensive, integrative program planning that considers, at a minimum, the future of current decisions, overall policy, organizational development, and links to operational plans.

Stratified Random Sampling
A sampling procedure for which the population is first divided into strata or subgroups based on designated criteria and then the sample is drawn, either proportionately or disproportionately, from each subgroup.

Structural Equation Modeling
A method for determining the extent to which data on a set of variables are consistent with hypotheses about causal association among the variables.

Structured Interview
An interview in which questions to be asked, their sequence, and detailed information to be gathered are all predetermined; used where maximum consistency across interviews and interviewees is needed.

Summative Evaluation
A type of outcome evaluation that assesses the results or outcomes of a program. This type of evaluation is concerned with a program's overall effectiveness.

Supplementary Variable
A variable upon which information is collected because of its potential relationship to a response variable.

Survey
The collection of information from a common group through interviews or the application of questionnaires to a representative sample of that group.

Surveys
Data collection techniques designed to collect standard information from a large number of subjects. Surveys may include polls, mailed questionnaires, telephone interviews, or face-to-face interviews.

Symmetric Measure of Association
A measure of association that does not make a distinction between independent and dependent variables.

Systematic Review
A synthesis of the research evidence on a particular topic, such as drug court effectiveness, obtained through an exhaustive literature search for all relevant studies using scientific strategies to minimize error associated with appraising the design and results of studies. A systematic review is more thorough than a literature review, but does not use the statistical techniques of a meta-analysis.

Systematic Sample
A sample drawn by taking every nth case from a list, after starting with a randomly selected case among the first n individuals.