Final answer:
Cross-sectional studies cannot establish causality, are prone to selection bias, and cannot measure changes over time. They are, however, not typically expensive to conduct, contrary to what's listed in the student's question.
Step-by-step explanation:
The disadvantages of cross-sectional studies include a few key limitations. Firstly, they cannot establish causality due to the nature of collecting data at a single point in time rather than across a time span. This means that even though a relationship between two variables may be observed, we cannot infer that one variable causes the other.
Another disadvantage is that cross-sectional studies are prone to selection bias. Since participants are selected at a single point in time, there may be inherent differences in the group that are not accounted for, which could affect the study's validity.
Additionally, cross-sectional studies cannot measure changes over time, because they offer only a snapshot rather than a continuous observation, making it impossible to observe trends or the progression of variables.
While it is mentioned that cross-sectional studies are generally less expensive and easier to conduct than longitudinal research, it is a misconception that they are costly. In fact, these types of studies are typically more budget-friendly when compared to other research methods such as cohort or case-control studies that follow subjects over a prolonged period.