Consider the following excerpt:
The efficacy of a brief prevention program (BP) aimed at arresting the development of chronic post-traumatic stress disorder (PTSD) was examined with 10 recent remale victims of sexual and nonsexual assault who received 4 sessions of a cognitive-behavioral program shortly after the assault. Their PTSD and depression severity was compared with that of 10 matched recent female assault victims who received repeated assessments of their trauma-related psychopathology (assessment control: AC). The BP program consisted of education about common reactions to assault and cognitive-behavioral procedures.
What is the independent variable? How many levels does it have?
What is/are the dependent variables?
What is the scientific hypothesis?
What is the null hypothesis?
Explain why the internal validity of this study is relatively low.
How does low internal validity affect our interpretation of the results of this study?
Identify two strategies of control that were used in this research.
Independent variable: brief prevention program versus no brief prevention program (control); 2 levelsdependent variables: ptsd and depression severityscientific hypothesis: people who participate in the brief prevention program will have lower ptsd and depression severity.null hypothesis: there will be no difference between participants in the brief prevention program and those in the control group in ptsd or depression severity. (no effect of the brief prevention program on ptsd or depression severity)the internal validity of this study is relatively low because participants were not randomly assigned to conditions. thus, there is a selection threat to the internal validity of this study.the low internal validity of this study means that we cannot draw causal conclusions about the effect of the brief prevention program on ptsd and depression severity. that is, we cannot conclude that the brief prevention program caused lower ptsd and less severe depression.two strategies of control: limiting the population and matching.