Controlled Experiment
Controlled Experiment is a test where you change one thing and keep everything else the same to see what happens.
You bake two batches of cookies at the same time. Both use the same dough, the same pan, and the same oven heat. The only change is baking time — one batch bakes for 10 minutes, the other for 15. When you compare the two trays, any change in color or texture comes from that one difference alone.
Explaining controlled experiment by grade level
Think about testing if exercise helps you do better on a test. You have two groups take the same test. One group exercises first. The other group sits quietly. You keep the test, the room, and the time the same. Only the exercise part changes. That way you know exercise made the difference.
Projects that explore controlled experiment
A controlled experiment changes one thing and keeps everything else the same. Here, the one change is whether participants exercise before the exam. Each subject has two papers of equal difficulty, so the only difference between test days is the 30 minutes of light activity — jogging or walking — before Paper B. Everything else stays constant: the subjects, the participants, the difficulty level.
Keeping everything else the same is what makes a controlled experiment trustworthy. Here, each participant faces passages "of equal difficulty" and the same 50-question format. The single change is the method of intake: reading versus listening. That isolation reveals which method leads to better comprehension scores.
A controlled experiment changes one thing and keeps everything else the same. Each participant takes an exam before any gaming, then takes a second exam of equal difficulty after 14 days of daily video game play. The person, the study notes, and the exam difficulty stay constant. Only the gaming exposure changes — making it possible to compare each person's scores before and after the two weeks.