Which of the following describes an experimental study?

An experimental study is characterized by the active manipulation of an independent variable to observe its effects on a dependent variable. The essence of this type of research is the implementation of a specific intervention or treatment that is applied to a group, while typically comparing it to a control group that does not receive the intervention. This allows researchers to establish causal relationships by determining how changes in the independent variable (the intervention) influence the dependent variable (the outcome being measured).

In this context, the option that describes an experimental study involves the administration of an intervention to one group only. This approach can be part of a larger experimental design, often in conjunction with a control group for comparative purposes. However, the key element here is the intervention itself, which is fundamental to the definition of an experimental study.

The other options do not fit the framework of an experimental study. Non-experimental observational studies gather data without manipulating any variables. A case study analysis focuses on an in-depth exploration of a single instance or subject, often lacking the broader application typically associated with experimental studies. A longitudinal study tracks the same subjects over time but does not necessarily involve experimental manipulation of variables. Each of these designs has its own merits and uses but does not adhere to the fundamental principles of experimental research,