An experiment or controlled experiment is a data collection method used in statistical research to measure the effect of some treatment. It divides a sample into two groups that are kept under the same conditions. One group — the treatment group — receives some type of treatment, while the other — the control group — does not receive any treatment.

Experiments are used in statistical studies to compare the effect on the treatment group to the control group. For example, suppose a medical center wants to test whether a new vaccine helps defeat breast cancer in women. To conduct a controlled experiment, researchers need to sample women with breast cancer and randomly assign them to groups.

Control Group	Treatment Group
Women with breast cancer that will not receive the vaccine.	Women with breast cancer that will receive the vaccine.

In a controlled experiment, the treatment can be any action that can affect a variable under study. For example, vaccinations given to people, fertilizers applied to crops, and education through online videos are all treatments. Lastly, it is crucial to understand that controlled experiments have both advantages and disadvantages. Always consider the advantages and disadvantages carefully when performing an experiment, taking into account the context and situation being studied.