Designing a controlled study
Build a fair test: one thing changed on purpose, everything else held steady, and a group to compare against.
- Writing a testable question: A controlled study answers a question you can actually measure, which has to be written first.
- Making a fair comparison: Designing controls depends on knowing that two groups must start the same to be compared fairly.
Prerequisites are inferred: pending teacher review.
Re-learn the skill with worked practice and clear examples.
A controlled study changes one factor on purpose, holds every other factor steady, and uses a control group that doesn't get the change so you can tell the change caused the result.
A team studies whether a 5-minute warm-up speeds heart-rate recovery. Group A warms up then runs; Group B just runs. Both groups run the same distance at the same pace in the same room, and both groups are similar in fitness. What is the role of Group B?
Reviewed- A.It is the controlled variable
- B.It is the control group used for comparison
- C.It is a confounding factor
- D.It is the hypothesis
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Answer: B. It is the control group used for comparison
- Step 1: Find what's being compared: Group A gets the change (warm-up); Group B does not.
- Step 2: Name the no-change group: The group that does the routine without the change, used to compare against, is the control group.
Why it's right: Group B does everything the same except the warm-up, so it is the control group that the treated group is compared against.
- A: A controlled variable is a factor held the same (like distance or pace), not a group.
- C: A confounding factor is an unwanted difference between groups, not the comparison group itself.
- D: A hypothesis is the prediction being tested, not a group of subjects.
Aligned to Biomedical Innovation: controlled study design · reading level ~grade 9
- A physiology team keeps a setup checklist so both groups get identical conditions except the one factor under test.
Fill these in as you work through the lesson.
- Hypothesis (a testable, if-then prediction you can support or reject):
- Control group (the group that does not get the change, used for comparison):
- Controlled variable (a factor kept the same for every group):
- Confounding factor (an extra thing that differs between groups and could explain the result instead):
In a fair test you change only one on purpose, keep every other the same, and compare against a group that did not get the change.
- Why does a study need a control group instead of just testing the new treatment alone?
- What goes wrong if two groups differ in more than one way?
- Turn this into a hypothesis you could test: 'Does a heart-rate app help people exercise more?'
A team thinks a 5-minute warm-up lowers resting heart rate after exercise. Design a controlled study: state the hypothesis, name what you change, name what you hold steady, and describe the control group.