What is the effect of 'selection bias' on research studies?

Selection bias occurs when the participants included in a research study are not representative of the larger population that the researchers aim to analyze. This can happen due to systematic differences between the participants who are selected for the study and those who are not. As a result, the findings may not accurately reflect the characteristics or behaviors of the overall population.

When selection bias is present, it compromises the validity of the study's conclusions. The outcomes may be skewed or misleading because the sample does not appropriately mirror the demographic or behavioral features of the population in question. For instance, if a health study only includes participants who are already healthy, it will fail to capture the experiences and outcomes of individuals with various health conditions.

In summary, the impact of selection bias is detrimental because it can lead to incorrect assumptions about causality, correlation, or the overall effectiveness of an intervention, thereby undermining the validity of the research findings.