Searching for Evidence
Sources of Evidence
Glossary of Terms


Below are definitions for some of the words used in this website. We recognize these are not the only possible meanings. Italicized words in an entry are defined elsewhere in the glossary. For more complete information about these terms, consult Macgowan (2008).

Applicability.  How relevant, suitable, and supportable an intervention/technique is for a particular clinical situation. Applicability is related to external validity, which is defined as “the extent to which the findings of a study are relevant to subjects and settings beyond those in the study” (Vogt, 1999, p. 105). Studies that are more likely to have conditions representing real world practice settings have better external validity than those that cannot be created outside the context of the research study. To evaluate the evidence’s applicability, the group worker compares information from a study and compares it with the worker’s own situation in three areas: Agency setting, leader variable, and group variables. For more information, consult Macgowan (2008).

Authority-based evidence. “The opinions of others, pronouncements of ‘authorities,’ unchecked intuition, anecdotal experience, and popularity (the authority of the crowd)” (Gambrill, 1999, p. 7). These sources tend to have higher bias than research-based evidence and are generally less reliable for answering causal-type questions, such as “what is the likelihood of an action leading to a desired outcome?” However, in some cases in which research evidence is unavailable, authoritative evidence may be the only source (Macgowan, 2008). Such evidence must be evaluated for its quality (for guides for evaluating authority-based evidence in group work, see Macgowan, 2008) 

Best evidence, best available evidence. “Best” evidence is knowledge that “yields documentary support for the conclusion that a practice or service has a reasonable probability of effectiveness” (Cournoyer, 2004, p. 14). It is evidence that has been acquired after a systematic search and that has been critically reviewed for its research merit, impact, and applicability (Macgowan, 2008). Best “available” evidence is evidence that has been acquired after a systematic search and a critical review, but the term acknowledges that there may be limitations on the quality of the evidence. For example, a research study (the evidence) may lack research merit but it may be the only relevant study available. 

Evidence. We adopt a broad definition and consider evidence, “unobserved as well as observed phenomena if the former reflects signs or indication that support, substantiate, or prove their existence, accuracy, or truth” (Cournoyer, 2004, p. 4). The term is not limited to information derived only through observation or experience (i.e. empirical or research evidence), but through many sources. However, there are degrees on the quality of evidence, see “best evidence.” The preference is for research evidence, if available, rather than authority-based evidence.

Evidence-Based Group Work (EBGW). “A process of the judicious and skillful application in group work of the best evidence, based on research merit, impact, and applicability, using evaluation to ensure desired results are achieved” (Macgowan, 2008, p. 3). EBGW is operationalized through a sequence of four stages in which group workers 1) formulate an answerable practice question; 2) search for evidence; 3) undertake a critical review of the evidence (with respect to research merit, impact, and applicability), which yields the best available evidence; and 4) apply the evidence with judgment, skill, and concern for relevance and appropriateness for the group, utilizing evaluation to determine if desired outcomes are achieved. The logo on the website summarizes the major features of EBGW. The four hash marks indicate the four stages, and the subtitle – “science meets practice” – suggests that the process of EBGW attempts to effectively blend the two essential areas of professional group work.  

Group work. “Goal-directed activity with small treatment and task groups aimed at meeting socioemotional needs and accomplishing tasks. This activity is directed to individual members of a group and to the group as a whole within a system of service delivery" (Toseland & Rivas, 2005, p. 12). According to this definition, group work may involve treatment and task groups. Task groups are those “in which the overriding purpose is to accomplish a goal that is neither intrinsically nor immediately linked to the needs of the members of the group” (Toseland & Rivas, 2005, p. 14). Treatment groups are those whose major purpose is to meet members’ socioemotional needs (Toseland & Rivas, 2005, p. 14). Treatment groups are the context in which the common terms “group treatment,” “group therapy,” “group psychotherapy,” and “group counseling” is done.

Impact. The strength and direction of research findings or the recommendations of a study. Studies with the best impact demonstrate both statistical and substantive significant findings; i.e., strong, positive, and meaningful change among group members. Impact can be evaluated using one of the measures outlined in Macgowan (2008).

Research evidence. Evidence generated through formal, systematic research study. It can include quantitative and/or qualitative methods. The value of research evidence is that it has gone through a process to minimize biases, which is a major drawback of authority-based evidence. However, not all research evidence is equal. Some research evidence can be derived from poorly executed studies with high bias. Thus, it is essential to evaluate the research merit of all research evidence (numerous guides for evaluating research evidence in group work are in Macgowan, 2008). Examples of strong quantitative research evidence include systematic reviews of high quality research published in reputable, peer-reviewed journals, and expert panel opinions based on such reviews. Much of the material included in the links in this website is to quantitative research evidence.

Research merit, research rigor. A measure of the quality of research, including quantitative and qualitative. To evaluate research merit, group workers can use the numerous guides detailed in Macgowan (2008).


Cournoyer, B. R. (2004). The evidence-based social work (EBSW) skills book. Boston, Mass.: Allyn & Bacon.

Gambrill, E. (1999). Evidence-based clinical practice: An alternative to authority-based practice. Families in society, 80, 341-350.

Macgowan, M. J. (2008). A guide to evidence-based group work. New York: Oxford University Press.

Toseland, R. W., & Rivas, R. F. (2005). An introduction to group work practice (5th ed.). Boston: Pearson/Allyn and Bacon.

Vogt, W. P. (1999). Dictionary of statistics & methodology: A nontechnical guide for the social sciences (2nd ed.). Thousand Oaks, Calif.: Sage Publications.