Participants in a _____ can be followed repeatedly and sometimes over the span of years.

A panel study is characterized by its ability to track the same group of individuals over time, allowing researchers to capture data at multiple points and observe changes within the same population. This longitudinal approach offers valuable insights into how certain variables evolve and how earlier experiences or characteristics may influence later outcomes.

In panel studies, the repeated measurements taken from the same participants can reveal trends, patterns, and causal relationships that would not be as easily identifiable in cross-sectional designs, where data is collected at one point in time. This type of study is beneficial for assessing long-term effects and changes in behavior, attitudes, or conditions over years.

Other study types that are mentioned, such as cohort studies, also involve following a group of individuals but may not always focus on the same individuals for repeated measures. Trend studies observe changes in variables across different groups over time without necessarily studying the same individuals. Mixed method studies, on the other hand, combine qualitative and quantitative approaches but do not inherently imply a longitudinal focus. Therefore, the defining feature of a panel study is its ability to follow participants repeatedly, making it the correct answer in this context.