Which limitation might affect the validity of longitudinal studies?

The limitation that participants may drop out over time is significant in longitudinal studies because this attrition can lead to a biased sample. Over the course of a longitudinal study, individuals may leave for various reasons such as loss of interest, relocation, health issues, or other personal circumstances. This drop-out can affect the demographic representation of the remaining sample, making it less likely to reflect the original population. As a result, the findings may not be applicable to the broader group the study aims to represent, thereby impacting the overall validity of the conclusions drawn from the data.

In longitudinal research, retaining participants is crucial to maintaining the integrity of the data over time. If the characteristics of those who drop out differ systematically from those who remain, it can skew results and interpretations, leading researchers to incorrect inferences about changes over time. This concern highlights the importance of strategies geared toward participant retention throughout the study’s duration.

While other options may present challenges in research, they do not directly relate to the specific nature and impact of longitudinal studies as the issue of participant drop-out does.