Which of the following is not a characteristic of a retrospective study?

The option indicating that incidence rates may be computed is not typically a characteristic of a retrospective study. In retrospective studies, researchers analyze existing data collected in the past to investigate relationships between exposures and outcomes. Since individuals are selected based on outcomes that have already occurred, it limits the ability to observe new cases over time, which is essential for determining incidence—defined as the occurrence of new cases of a condition within a given time period.

In contrast, retrospective studies are generally conducive to estimating relative risk based on existing data, and they can be cost-effective since they utilize data that has already been collected, saving time and resources. However, while they can highlight associations, the assessment of past exposures does carry the risk of biases, such as recall bias or selection bias, due to the reliance on historical data and participants' memories.