Internal Validity In Single-Case Design Essay

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Internal validity of a research design is extremely important for the interpretation of results. There are various threats to internal validity in single-case designs (SCD) that Kratochwill (2010) discusses. Three threats of internal validity include selection, history, and maturation.
Selection refers to the participants selected for the study. If the participants characteristics are very different than it may affect the internal validity. Selection may affect SCDs that have two or more between-case intervention conditions that include groups. These groups could potentially change in size over time, affecting the grouping process. The size may change due to participants leaving the study, which could compromise how the treatment was understood …show more content…

The researchers do not know what may have occurred in the past to affect the treatment results, also during treatment a single outside event could affect the outcome of the study. Also, the participant or participants parents might be making other choices during time of treatment that may affect the outcome of the study in positive or negative ways (Kratochwill, 2010). If a participant was in the study due to lack of speech but also going to ABA therapy and speech classes during the time of the treatment, there would be now way to knowing if the outcome was due to the ABA, speech, or treatment intervention. Another internal validity threat is maturity of the participants. During a study, the participants may be going through natural maturity phases that could affect the intervention results. In SCDs research can be conducted over periods of time, such as; days, week, months, or even years, which allows participants time to change and mature overtime (Kratochwill, 2010). If a female starts in a treatment study at age 10 and continues on through age 13, she will likely be going through some major changes of puberty during that time that could have an affect on the internal validity of the treatment

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