Here's why:

* The scientific method: The scientific method is a systematic process for investigating phenomena and gaining new knowledge. It typically involves these steps:

* Observation: Noticing a phenomenon or pattern.

* Question: Formulating a question about the observation.

* Hypothesis: Developing a testable explanation for the observation.

* Prediction: Making a specific, measurable prediction based on the hypothesis.

* Experiment: Designing and conducting an experiment to test the prediction.

* Data Analysis: Analyzing the data collected during the experiment.

* Conclusion: Drawing a conclusion based on the data analysis, whether the hypothesis is supported or not.

* Control and experimental groups: A control group is a group that does not receive the treatment or manipulation being tested. An experimental group receives the treatment. By comparing the data from these two groups, scientists can determine if the treatment had an effect.

Therefore, comparing data from a control and experimental group is part of the data analysis stage of the scientific method.