Read the article in Appendix A “Example of a Randomized Clinical Trial” (Nyamathi et al.,2015), Discuss the following questions related to the article found on ~p. 162 under Critical Appraisal Criteria: 1. Is the type of design used appropriate? Your rationale? 2. What are the threats to internal and external validity?

1. Is the type of design used appropriate? Your rationale?

The randomized clinical trial (RCT) design used in the study conducted by Nyamathi et al. (2015) is indeed appropriate for addressing research questions related to interventions and their effects on a specific population. RCTs are considered the gold standard for determining causal relationships between interventions and outcomes, as they involve the random allocation of participants into groups receiving different interventions or control conditions. This design ensures that any observed differences in outcomes between the groups can be attributed to the intervention rather than other factors.

In this study, the researchers aimed to evaluate the effectiveness of a mindfulness-based stress reduction (MBSR) program on reducing stress, enhancing coping skills, and improving overall quality of life among homeless adults with mental illnesses. The RCT design allowed them to randomly assign participants to either the MBSR intervention group or the control group, which received usual care. This random assignment helps minimize selection bias and increase the internal validity of the study.

Furthermore, the researchers implemented a waitlist control design, ensuring that all participants eventually had access to the MBSR intervention. This design accounts for ethical considerations and allows for a comparison between the intervention and control groups over time, providing valuable insights into the intervention’s effects. Overall, the RCT design used in this study is appropriate given its research aims and the need for causal inference.

2. What are the threats to internal and external validity?

Internal validity refers to the extent to which a study correctly demonstrates cause-and-effect relationships between the intervention and the outcome, while external validity relates to the generalizability of the study’s findings to other populations or settings. In the study by Nyamathi et al. (2015), several threats to both internal and external validity can be identified.

One threat to internal validity is the possibility of attrition bias. Participants dropping out or being lost to follow-up can introduce bias if their characteristics differ from those who remain in the study. This can affect the comparability of groups and the accuracy of the estimated intervention effects. The researchers addressed this threat by conducting intention-to-treat analyses, which include all participants regardless of their adherence or retention in the study. However, attrition could still introduce bias if there are differential dropouts between the MBSR intervention group and the control group.

Another threat to internal validity is measurement bias. The study relied on self-report measures to assess outcomes such as stress levels and quality of life. This introduces the possibility of social desirability bias or measurement error. Participants might inaccurately report their experiences or provide responses that they perceive as more socially acceptable. While efforts were made to use validated instruments and establish their reliability, the potential for measurement bias should be acknowledged.

Regarding external validity, one major threat is the sample’s characteristics and representativeness. The study was conducted with a specific population of homeless adults with mental illnesses, which might limit generalizability to other populations. The unique circumstances and challenges faced by homeless individuals could influence the effectiveness of the MBSR intervention differently than in other populations. Therefore, caution should be exercised when extrapolating these findings to different contexts or populations.

Another aspect influencing external validity is the setting in which the study was conducted. The research was conducted at two major shelters for homeless individuals in Los Angeles, California. The specific resources and support systems available in this setting might not be representative of all homeless shelters or communities. Thus, the findings might not generalize to other settings that have different resources and support structures in place.

In summary, while the RCT design used in the study by Nyamathi et al. (2015) is appropriate for addressing the research questions, it is essential to consider the threats to internal and external validity. These threats include attrition bias, measurement bias, and limitations in sample characteristics and setting representativeness. Addressing these threats enables a more accurate interpretation of the study’s findings and enhances their applicability to diverse populations and settings.