Data collection is a systematic method of obtaining, observing, measuring, and analyzing accurate information. An experimental study is a standard method of data collection that involves the manipulation of the samples by applying some form of treatment prior to data collection. It refers to manipulating one variable to determine its changes on another variable. The sample subjected to treatment is known as “experimental units.”

An example of the experimental method is a public clinical trial of a drug. For instance, to test the efficacy of a new drug effective in treating blood pressure, one needs to perform an experimental data collection. The new drug is given to a small number of randomly selected volunteers who suffer from chronic high blood pressure.One group of subjects is treated with specific doses of drugs or treatment methods, and a control group may be given a placebo. The subjects are monitored for a few weeks. The symptoms of disease treatment and after-effects of the drug are observed, and the data is collected. As this process involves modifying the subjects, it is categorized under the experimental method.

Another example is studying the effect of a particular fertilizer on the plant's growth. For this purpose, a few plants are taken and subjected to treatment with the new fertilizer. The growth of the plants is monitored daily for a few weeks, and the data is collected.