A guide for professional counselors and counseling researchers for calculating and interpreting Percent Improvement as an indicator of clinical significance is provided. Strategies for reporting findings are described and illustrated. Guidelines for contextualizing discussions of clinical significance within the boundaries of psychometric evidence…

The What Works Clearinghouse (WWC) is an initiative of the U.S. Department of Education's Institute of Education Sciences (IES), which was established under the Education Sciences Reform Act of 2002. It is an important part of IES's strategy to use rigorous and relevant research, evaluation, and statistics to improve the nation's education system.…

The What Works Clearinghouse (WWC) systematic review process is the basis of many of its products, enabling the WWC to use consistent, objective, and transparent standards and procedures in its reviews, while also ensuring comprehensive coverage of the relevant literature. The WWC systematic review process consists of five steps: (1) Developing…

This "What Works Clearinghouse Procedures and Standards Handbook (Version 3.0)" provides a detailed description of the standards and procedures of the What Works Clearinghouse (WWC). The remaining chapters of this Handbook are organized to take the reader through the basic steps that the WWC uses to develop a review protocol, identify…

This handbook describes the structure and processes that the What Works Clearinghouse (WWC) uses for its reviews, presenting in one place all the standards the WWC currently uses to assess research. The handbook will be revised as new standards are developed and major new features are finalized. A distinguishing feature of the WWC is that it does…

With its critical assessments of scientific evidence on the effectiveness of education programs, policies, and practices (referred to as "interventions"), and a range of products summarizing this evidence, the What Works Clearinghouse (WWC) is an important part of the Institute of Education Sciences' strategy to use rigorous and relevant…

Written by a social worker for social work students, this is a nuts and bolts guide to statistics that presents complex calculations and concepts in clear, easy-to-understand language. It includes numerous examples, data sets, and issues that students will encounter in social work practice. The first section introduces basic concepts and terms to…

A concise table is presented based on a general measure of magnitude of effect which allows direct determinations of statistical power over a practical range of values and alpha levels. The table also facilitates the setting of the research sample size needed to provide a given degree of power. (Author/CM)

The concept of statistical significance is explained, with specific numerical illustrations. (MNS)

When reporting results, researchers must not change predetermined significance levels. Such attempts to make results more significant are statistically inaccurate, illogical, and unethical. American Psychological Association standards for reporting significance should be more explicit. (CP)

The dangers of equating "statistical significance" with "real world" significance are summarized. When a finding is said to have "statistical significance," it means only that the same results would be likely to occur again if the study were repeated, not that the finding has any true personal or societal importance. (VW)

Statistical significance is not a sufficient condition for claiming a hypothesis has been supported. Constructive replications are more important. Statistically significant results may be meaningless while a sequence of nonsignificant results may be quite important. Gives advice on how to overcome some limitations of classifical statistical…

Designed for use with Research for Better Schools' evaluation system, this guide focuses upon basic concepts and statistical procedures applicable to specific research hypotheses emerging from evaluation questions. The first of three sections presents a discussion of descriptive statistics in terms of frequency, central tendency, variability, and…

Considers how if literacy is envisioned as a sort of competence in a set of social and intellectual practices, then scientific literacy must encompass the realization that "statistical significance," the cardinal arbiter of social scientific knowledge, was not born out of an immanent logic of mathematics but socially constructed and…

This article explains and illustrates the estimation of the power of statistical tests used to analyze data in early childhood special education research, and discusses advantages and disadvantages of various ways to increase power, such as using a directional alternate hypothesis or using a parametric, rather than nonparametric, statistical test.…