ESTABLISHING EVIDENCE-BASED PRACTICES IN DISABILITY SERVICES

Article presents the theoretical understanding of usage of evidence-based practices in disability service promoting the most effective of practices. The details of identifying, promoting, and implementing EBPs involve a plethora of potentially problematic issues. Detail discussed purports of quality and quantity of the research describes wide application fi eld of EBP. Criterion-based frameworks for determining effective or evidence-based practices could be used as a practical guide in disability services. The essential steps in determining whether a practice is evidence-based seem to be (a) locating the high quality, experimental research that examines the effectiveness of the practice and then (b) determining whether suffi cient quantity of evidence showing that the practice causes improved outcomes exists are discussed as well.


Problem of the research
A common concern among professionals who work with individuals with disabilities, their families, and the agencies that provide services to them is the gap between what research shows to be effective and what happens in day-to-day practices.Indeed, the research-topractice gap seems to be as similar a concern in special education as it does in speech therapy, in rehabilitation counseling, and in adapted physical education.
To bridge the research-to-practice gap, scholars have focused recently on identifying, promoting, and implementing evidence-based practices -instructional approaches, therapies, and interventions shown by high quality research to result reliably in generally improved outcomes for the client or student.An evidence-based practice is one that is supported by a body of trustworthy research that, taken as a whole, demonstrates that the practice is highly likely to meaningfully improve outcomes for individuals with disabilities (Cook, Tankersley, & Landrum, 2009).Determining which practices are evidence-based practices requires a systematic approach to identifying those that are supported by a suffi cient number of research studies that (a) are of high methodological quality, (b) use appropriate research designs that allow for assessment of effectiveness, and (c) demonstrate a meaningful body of results through which the cumulative results engender trust that the practice works (Cook et al., 2009).
The idea of evidence-based practices is not new, as criteria and standards for determining them have been developed and applied in other fi elds, most visibly in medicine (Sackett, Richardson, Rosenberg, & Haynes, 1997) and psychology (Chambless et al., 1998).Although 120

Quality of research
Determining the evidence-base of a practice not only requires that the research studies supporting the practice exhibit experimental control, but also that the studies are conducted with high quality.If research is not conducted properly, the results can be misleading at worse, or, at minimum, can be meaningless.Although there is not, as of yet, a clear consensus as to the methodological characteristics needed to ensure that experimental research in many disability service fi elds is rigorously conducted, several of the disability-focused disciplines have begun to propose or implement "quality indicators" for group experimental (Gersten et al., 2005; see Table1).Data Analysis 1. Were the data analysis techniques appropriately linked to key research questions and hypotheses?Were they appropriately linked to the unit of analysis in the study?2. Did the research report include not only inferential statistics but also effect size calculations?
At the same time several of the disability-focused disciplines have proposed or implemented "quality indicators" for single-subject research (Horner et al., 2005; see Table 2).Quality indicators are design characteristics that are important to address in order to have high confi dence in the fi ndings of the study.Said differently, using quality indicators of methodological quality, one can have the highest confi dence in the fi ndings of research studies that incorporate them into the designs; therefore, only high quality studies should be considered in determining whether a practice is evidence-based.
Certainly, the methodological rigor with which a study is conducted affects the confi dence one can place in its fi ndings.If the intervention was not implemented as designed, no meaningful conclusion can be drawn as to the effectiveness of the practice.To establish evidence-based practices for disability services, one of the fi rst tasks of the research community must be to agree upon and systematically apply a set of quality indicators for methodological rigor, like those proposed by Gersten et al. (2005) and Horner et al. (2005), so that the quality of the research surrounding a practice can be evaluated.

Independent Variable
1. Independent variable is described with replicable precision.2. IV is systematically manipulated and under the control of the experimenter.
3. Overt measurement of the fi delity of implementation for the independent variable is highly desirable.
Baseline 1.The majority of single-subject research studies will include a baseline phase that provides repeated measurement of a dependent variable and establishes a pattern of responding that can be used to predict the pattern of future performance, if introduction or manipulation of the independent variable did not occur.2. Baseline conditions are described with replicable precision.

Experimental Control/Internal Validity
1.The design provides at least three demonstrations of experimental effect at three different points in time.2. The design controls for common threats to internal validity (e.g., permits elimination of rival hypothesis) 3. The results document a pattern that demonstrates experimental control.

External Validity
1. Experimental effects are replicated across participants, settings, or materials to establish external validity.

Social Validity
1.The dependent variable is socially important.
2. The magnitude of change in the DV resulting from the intervention is socially important 3. Implementation of the IV is practical and cost-effective.4. Social validity is enhanced by implementation of the IV over extended time periods, by typical intervention agents, in typical physical and social contexts. 122

Quantity of research
Determining evidence-based practices relies on the accumulation of results over time and over different research conditions (e.g., geographic regions, research teams, settings).The accumulation of results that converge toward a generalization of effectiveness provides more confi dence than the results of a single study -even if that single study is approached with the highest of rigor and results in a large effect size.
Multiple high quality, experimental studies are needed to conclude that a practice is evidence-based.For example, in special education, Gersten et  Other disability service fi elds have also developed and implemented criterion-based frameworks for determining effective or evidence-based practices.For example, the Division 12 Task Force of the American Psychological Association (APA) recommended that for a treatment to be considered well-established, at least one of two empirical criteria must be met (Chambless et al., 1998): 1. Two or more good group design experiments must demonstrate that the treatment is either (a) signifi cantly superior to pill, placebo, or other treatment, or (b) equivalent to a previously established treatment.
2. More than nine single-subject studies demonstrating experimental design and favorably comparing the intervention to another treatment.
Applied research cannot provide absolute proof that an intervention is effective.Instead, the fi ndings of an experimental study can either add support to or weaken the hypothesis that a practice causes meaningful changes in individual outcomes.The more high-quality experimental studies that support a practice, the greater the confi dence we have that it causes desired changes.And the more high quality experimental studies that provide consistent fi ndings regarding effectiveness, the greater confi dence we have in determining the practice to be evidence-based.

What does being an evidence-based practice mean?
The essential steps in determining whether a practice is evidence-based seem to be (a) locating the high quality, experimental research that examines the effectiveness of the practice and then (b) determining whether suffi cient quantity of evidence showing that the practice causes improved outcomes exists.
Being evidence-based does not mean that a practice is guaranteed to work for every individual in every situation (Cook, Smith, & Tankersley, 2011).For example, the fi ndings from a group experimental study might demonstrate that individuals who received an intervention achieved superior outcomes on average in comparison to similar individuals in the control group who did not receive the intervention.That does not mean that every individual in the experimental group excelled following the implementation of the practice.However, despite this caution, when implemented as designed, we can be confi dent that evidence-based practices provide the highest likelihood of improving outcomes.To use a gambling analogy, implementing an evidence-based practice is similar to placing a bet that is, say, 95% likely to pay off; whereas, implementing a practice shown by research not to be evidence-based may have, for example, only a 50% chance of paying off.Even though a pay off is not guaranteed

Melody Tankersley
with either strategy, it is clear which is the best bet in the high stakes game of disability services (Cook, Tankersley, Cook, & Landrum, 2008).Accordingly, evidence-based practices should be the fi rst option for practitioners who want to improve outcomes of individuals with disabilities.

Conclusion
Practitioners make the ultimate determination regarding the interventions that individuals with disabilities receive.It is imperative that we use the most effective practices, and that the fi elds of disability services identify what those practices are so that practitioners can have the greatest impact.As Hammersley (2005) asked, "Who would want…practice not to be based on evidence?"(p.86).The fi elds of disability services are beginning to identify and stress the implementation of evidence-based practices.Although much important work lies ahead for disability service researchers and practitioners, we will approach these tasks with an optimistic enthusiasm for it is evidence-based practices that provide our students, clients, friends, and family members the best chance of success.

Melody Tankersley, Kent State University, USA
The idea of evidence-based practices is not new, as criteria and standards for determining them have been developed and applied in other fi elds, most visibly in medicine and psychology.Although the use of evidence-based practices in disability services appears to hold great promise for promoting the most effective of practices, and, upon fi rst consideration, even seems to be a straightforward enterprise, the details of identifying, promoting, and implementing EBPs involves a plethora of potentially problematic issues.For example, questions regarding the types of research designs that can identify evidence-based practices, how many research studies are needed to identify a practice as evidencebased, and how methodological quality can be assessed are among the fi rst questions that must be answered in order to determine which practices are evidence-based.
Determining which practices are evidence-based practices requires a systematic approach to identifying those that are supported by a suffi cient number of research studies that (a) are of high methodological quality, (b) use appropriate research designs that allow for assessment of effectiveness, and (c) demonstrate a meaningful body of results through which the cumulative results engender trust that the practice works.
Certainly, the methodological rigor with which a study is conducted affects the confi dence one can place in its fi ndings.If the intervention was not implemented as designed, no meaningful conclusion can be drawn as to the effectiveness of the practice.To establish evidence-based practices for disability services, one of the fi rst tasks of the research community must be to agree upon and systematically apply a set of quality indicators for methodological rigor, so that the quality of the research surrounding a practice can be evaluated.
al. (2005) recommended that at least 4 acceptable quality studies or 2 high quality group experimental studies support an evidence-based practice while Horner et al. (2005) recommended that 5 high quality singlesubject research studies support an evidence-based practice.Horner et al.'s recommendation further qualifi ed that to be considered evidence-based on the basis of single-subject research, the practice's minimum of fi ve high quality single-subject studies must (a) be conducted by at least three different researchers in at least three different locations and (b) includes a total of at least 20 participants.

Table 2 .
Essential quality indicators of single-subject designs proposed by Horner et al. (2005) Describing Participants and Settings 1. Participants described with suffi cient detail to allow others to select individuals with similar characteristics (e.g., age, gender, disability, diagnosis).2. The process for selecting participants is described with replicable precision.3. Critical features of the physical setting are described with suffi cient precision to allow replication.Measurement of the dependent variable is valid and described with replicable precision.4. Dependent variables are measured repeatedly over time. 5. Data are collected on the reliability of interobserver agreement associated with each dependent variable, and IOA levels meet minimal standards (e.g., IOA = 80%, Kappa = 60%).