What threat to internal or external validity
does this statement suggest: “It’s a good thing
that I’m in this new diet study. I couldn’t believe
it when the researcher told me that I was 10 lbs.
overweight.”
The Correct Answer and Explanation is :
The statement, “It’s a good thing that I’m in this new diet study. I couldn’t believe it when the researcher told me that I was 10 lbs. overweight,” suggests a threat to internal validity known as selection bias. This occurs when participants self-select into a study based on certain characteristics, such as being overweight, which can influence the study’s outcomes.
Explanation:
In research, internal validity refers to the degree to which an experiment accurately measures the effect of the independent variable on the dependent variable, without interference from other variables. Selection bias is a threat to internal validity that arises when participants choose to join a study based on specific traits or conditions, leading to a sample that is not representative of the general population.
In the given statement, the participant expresses surprise upon learning they are 10 pounds overweight, suggesting they were unaware of their weight status before the study. This implies that the participant may have self-selected into the diet study without prior knowledge of their weight, potentially because they were unaware of being overweight. Such self-selection can lead to a sample that is not representative of the broader population, as individuals who are unaware of their weight status might be more likely to participate in diet studies.
This self-selection introduces selection bias, as the study sample may overrepresent individuals who are unaware of their weight status, potentially affecting the generalizability of the study’s findings. For instance, if the study aims to assess the effectiveness of a diet intervention for overweight individuals, the results might not accurately reflect the broader population of overweight individuals, as those who are unaware of their weight status may respond differently to the intervention.
To mitigate selection bias, researchers can implement random sampling techniques, ensuring that every individual in the target population has an equal chance of being selected for the study. Additionally, providing participants with information about their weight status before enrollment can help ensure that the study sample accurately represents the target population, thereby enhancing the internal validity of the research.
In summary, the participant’s statement highlights a potential selection bias threat to internal validity, emphasizing the importance of representative sampling and informed participant selection in research design.