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Very late onset schizophrenia affects people who are at least 60 years old. In a 2018 study reported in The Lancet Psychiatry, researchers conducted a double-blind controlled experiment to study the effect of the drug amisulpride on these patients (Howard et al., 2018 ). The experiment was divided into two stages, and subjects were randomly assigned to one of three groups: Group 1 received the drug for both stages, Group 2 received the drug for stage 1 and the placebo for stage 2, and Group 3 received the placebo for state 1 and the drug for stage \(2 .\) Researchers found that those subjects receiving the drug showed reduced psychosis symptoms compared with those receiving the placebo. a. Identify the treatment and response variables. b. Restate the conclusion of the study in terms of a cause-and-effect conclusion. Why can a cause-and-effect conclusion be made from this study?

Step by step solution

01

Identifying the Treatment Variables

In this experiment, the treatment variables are the drugs given to each group. There are three groups, each having different conditions - Group 1 received the drug during both stages, Group 2 received the drug during the first stage and a placebo during stage 2, and Group 3 received a placebo during stage 1 and the drug during stage 2.

02

Identifying the Response Variables

The response variable in this study is the reduction of psychosis symptoms in subjects. The level of this variable indicates the effectiveness of the drug. Researchers quantify the change in psychosis symptoms to measure the impact of the drug (the treatment).

03

Restating the Conclusion in Terms of Cause-and-Effect

The cause-and-effect conclusion that can be drawn from this study is that the drug amisulpride reduces the symptoms of psychosis in patients with very late onset schizophrenia. This conclusion can be made since this is a controlled, double-blind experiment, where the treatment groups were randomly assigned, thus minimizing potential bias and making it possible to infer causality from the observed effects.

04

Explanation of Cause-and-Effect Conclusion

The cause-and-effect conclusion can be made based on the design of this experimental study. The random assignment of subjects takes care of potential confounding variables that could affect the outcome. Furthermore, the double-blind nature of the study ensures that neither the researchers nor the participants could affect the results based on their knowledge of the treatment. Thus, it enables the establishment of a causal relationship between the drug and the reduction in psychosis symptoms.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Treatment Variables

In the context of statistical experiment design, treatment variables are the factors or conditions that are manipulated by the experimenters to determine their effect on a particular outcome. In this study focused on very late onset schizophrenia, the treatment variable is the administration of the drug amisulpride. The study involved three groups with different instructions on drug intake:

• Group 1 received amisulpride during both stages of the experiment, providing a continuous exposure to the treatment.
• Group 2 took the drug only during the first stage and switched to a placebo in the second stage. This allows for an analysis of the drug's short-term and withdrawal effects.
• Group 3 started with a placebo in stage one and received the drug in the second stage, providing comparative data on initial placebo effects followed by treatment effects.

These different treatment regimens enable researchers to isolate the drug's effects over time, on both initiation and withdrawal phases, providing a comprehensive understanding of its efficacy and dynamics.

Response Variables

Response variables are outcomes or effects measured in an experiment to assess the impact of treatment variables. In this study, the primary response variable is the reduction in psychosis symptoms among patients. This reduction is quantified through various clinical assessments. The changes in symptoms are monitored to track the efficacy of the treatment.

The researchers aim to see how the different approaches to administering amisulpride affect these symptoms. Here's how the response variables are interpreted in this context:

• A significant reduction in symptoms among those receiving amisulpride indicates a positive response to the treatment.
• Comparing symptom reduction between stages and across different groups helps analyze both short-term and long-term drug efficacy.
• The variation in symptom improvement between drug and placebo stages provides insights into the drug's specific impact versus generic placebo effects.

By focusing on these changes in psychosis symptoms, researchers can evaluate the direct impact of amisulpride as the main operative factor in patient improvement.

Cause-and-Effect Conclusion

The study design allows researchers to draw a cause-and-effect conclusion about the effectiveness of amisulpride. The rigorous setup involves both double-blind and random assignment approaches that enhance the reliability of results.

Here’s why this particular study can rest on a sound cause-and-effect conclusion:

• Random Assignment: Subjects were randomly placed into treatment groups, which helps distribute confounding factors evenly across groups, reducing selection bias.
• Double-Blind Design: Neither the participants nor the researchers knew who received the drug or placebo, which minimizes bias and the placebo effect.
• Controlled Environment: By maintaining control over extraneous variables, the study ensures that changes in the response variable are likely due to the treatment itself rather than outside influences.

By effectively controlling these factors, the study provides strong evidence that the administration of amisulpride causes a reduction in psychosis symptoms, illustrating a direct causal relationship between the treatment and observed effects. This robust methodological approach supports the validity of drawing such cause-and-effect inferences.