Which type of study involves the investigator actively changing factors to observe outcomes?

An experimental study is characterized by the investigator actively intervening and manipulating one or more variables to observe the effects on certain outcomes. This type of research design aims to establish cause-and-effect relationships by controlling other variables that could potentially influence the results. In an experimental study, participants are often assigned to different groups, such as treatment and control groups, to measure the specific impact of the intervention being tested.

In contrast, a cross-sectional study captures data at a single point in time to examine relationships among variables without any manipulation, making it more observational in nature. A retrospective study looks back at data collected in the past to identify trends or associations, rather than involving active intervention. A prospective study follows participants over time to observe outcomes based on exposures or interventions, but it does not involve actively changing variables by the researcher. Thus, the key differentiator for experimental studies is the intentional manipulation of variables to directly assess their impact on outcomes.