Several challenges can arise during sample selection, including:
Selection Bias: Occurs when certain individuals are more likely to be selected than others, leading to non-representative samples. Non-response Bias: Happens when individuals who do not participate differ significantly from those who do, potentially skewing results. Loss to Follow-up: In longitudinal studies, some participants may drop out, which can affect the studyâs validity if the dropouts differ from those who remain.
