What is the difference between descriptive research and experimental research?

Descriptive research answers the (what questions) it's used to describe something like size, quantity, etc.. While an experimental research is about testing and changing conditions to reach to a specific reaction or to answer why, how and when questions

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in experimental research, you have some parameters on which you have a control. using these parameters, you find the answer to the quantity you want. while in descriptive research, you look for methods such as case studies. if you read environmental studies, you will see several case studies and the impact of these and the lessons you learned from that. especially realted to how some incident lead to pollution etc