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Backfill Techniques
Techniques used in cumulative case studies to collect information needed if the study is to be usable for aggregation; these techniques include, for example, obtaining missing information from the authors on how instances studied were identified and selected.

Baseline Data
Initial information on a program or program components collected prior to receipt of services or participation activities. Baseline data are often gathered through intake interviews and observations and are used later for comparing measures that determine changes in a program.

Batch
A group of cases for which no assumptions are made about how the cases are selected. A batch may be a population, a probability sample, or a nonprobability sample, but the data are analyzed as if the origin of the data is not known.

Before-After Designs
The elementary quasi-experimental design known as the before-after design involves the measurement of "outcome" indicators (e.g., arrest rates, attitudes) prior to implementation of the treatment, and subsequent re-measurement after implementation. Any change in the measure is attributed to the treatment. This design provides a significant improvement over the one-shot study because it measures change in the factor(s) to be impacted. However, this design suffers from threats of history - the possibility that some alternate factor (besides the treatment) has actually caused the change.

Bell-Shaped Curve
A distribution with roughly the shape of a bell; often used in reference to the normal distribution but others, such as the t distribution, are also bell-shaped.

Benchmarking
Measuring progress toward a goal at intervals prior to the anticipated attainment of the goal. FOR EXAMPLE, measuring and tracking grade-level performance of students in a remedial program at intervals prior to completion of the program.

Benchmarks
Measures of progress toward a goal, taken at intervals prior to the program's completion or the anticipated attainment of the final goal. FOR EXAMPLE, semi-annual measures of grade-level performance taken prior to completion of a remedial education program.

Between-Group Variances
Indications of how the mean and variances of each group differ from the other groups.

Bias
The extent to which a measurement, sampling, or analytic method systematically underestimates or overestimates the true value of an attribute. FOR EXAMPLE, words, sentence structure, attitudes, and mannerisms may unfairly influence a respondent's answer to a question. Bias in questionnaire data can stem from a variety of other factors, including choice of words, sentence structure, and the sequence of questions.

Biased Sample
A sample that is not representative of the population to which generalizations are to be made. FOR EXAMPLE, a group of band students would not be representative of all students at the middle school, and thus would constitute a biased sample if the intent was to generalize to all middle school students.

Binary Variables
A variable that identifies the presence or absence of a trait, characteristic, opinion, etc.; a "yes/no" variables. FOR EXAMPLE, Male - 0=No, 1=Yes.

Bivariate Analysis
An analysis of the relationship between two variables. FOR EXAMPLE, an analysis of the relationship between sex (male/female) and delinquent activity, taking no other factors into account.

Bivariate Data
Information about two variables.

Box-and-Whisker Plot
A graphic way of depicting the shape of a distribution.



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