AB+-+Dimitrov+&+Rumrill+(2003)

Internal validity is the degree to which the experimental treatment makes a difference in (or causes change in) the specific experimental settings. External validity is the degree to which the treatment effect can be generalized across populations, settings, treatment variables, and measurement instruments. . . . Factors that threaten internal validity are: history, maturation, pretest effects, instruments, statistical regression toward the mean, differential selection of participants, mortality, and interactions of factors. . . . Threats to external validity include: interaction effects of selection biases and treatment, reactive interaction effect of pretesting, reactive effect of experimental procedures, and multiple-treatment interference. ( p. 159 ) The use of a nonrandomized control group pretest-posttest design has the practical advantage that “ it deals with intact groups and thus does not disrupt the existing research setting ” ( p. 160 ) which improves the external validity by reducing “ the reactive effects of the experimental procedure ” ( p. 160 ), but potentially dilutes the internal validity because of “ selection and maturation, selection and history, and selection and pretesting ” ( p. 160 <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">). The authors suggest that for a nonrandomized control group design the comparison groups are not assumed to be equal on the pretest, and “the data analysis with this design should use ANCOVA or other appropriate statistical procedure” ( <span style="font-family: 'Times New Roman',Times,serif; font-size: 90%;">p. 163 <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">) but if the pretest scores are not reliable “ <span style="color: #0000ff; font-family: 'Times New Roman',Times,serif; font-size: 120%;">the treatment effects can be seriously biased <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">” ( <span style="font-family: 'Times New Roman',Times,serif; font-size: 90%;">p. 164 <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">) in a nonrandomized design. ||
 * **<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">Reference: ** || <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Dimitrov, D. M., & Rumrill, P. D. Jr. (2003). Pretest-posttest designs and measurement of change. //Work, 20//(2), 159-165. Retrieved from http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCoQFjAA&url=http%3A%2F%2Fwww.phys.lsu.edu%2Ffaculty%2Fbrowne%2FMNS_Seminar%2FJournalArticles%2FPretest-posttest_design.pdf&ei=Z0V1T4rLJ8Wi2gXum-mUDQ&usg=AFQjCNF6-c4j-7JJKm9ohkXr6jXJ1T-7pA&sig2=BW7hMizEWzQBfgUIIQ30rA ||
 * **<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">Author's: ** || <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Dimitrov, D. M., & Rumrill, P. D. Jr. ||
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">**Title:** || <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Pretest-posttest designs and measurement of change. ||
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">**Year:** || <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">2003 ||
 * **<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">Journal: ** || //<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Work // ||
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">**Retrieval Information**: || <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCoQFjAA&url=http%3A%2F%2Fwww.phys.lsu.edu%2Ffaculty%2Fbrowne%2FMNS_Seminar%2FJournalArticles%2FPretest-posttest_design.pdf&ei=Z0V1T4rLJ8Wi2gXum-mUDQ&usg=AFQjCNF6-c4j-7JJKm9ohkXr6jXJ1T-7pA&sig2=BW7hMizEWzQBfgUIIQ30rA ||
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">**Bibliography**: ||  ||
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">The underlying context of this article is rehabilitation services and the use of pretest-posttest designs in that field. I am more interested in the discussion of the research design and its related reliability issues.
 * **<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">Journal: ** || //<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">Work // ||
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">**Retrieval Information**: || <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCoQFjAA&url=http%3A%2F%2Fwww.phys.lsu.edu%2Ffaculty%2Fbrowne%2FMNS_Seminar%2FJournalArticles%2FPretest-posttest_design.pdf&ei=Z0V1T4rLJ8Wi2gXum-mUDQ&usg=AFQjCNF6-c4j-7JJKm9ohkXr6jXJ1T-7pA&sig2=BW7hMizEWzQBfgUIIQ30rA ||
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">**Bibliography**: ||  ||
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">The underlying context of this article is rehabilitation services and the use of pretest-posttest designs in that field. I am more interested in the discussion of the research design and its related reliability issues.
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">**Bibliography**: ||  ||
 * <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">The underlying context of this article is rehabilitation services and the use of pretest-posttest designs in that field. I am more interested in the discussion of the research design and its related reliability issues.
 * **<span style="font-family: 'Times New Roman',Times,serif; font-size: 130%;">Additional References: ** ||  ||
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