Identify Variables and Controls
Sort what changes, what is measured, what stays the same, and what comparison group is used.
- Read a data table: Students need to find values, labels, and units before calculating or graphing.
- Fair-test logic: Variables and controls make comparisons meaningful.
Prerequisites are inferred: pending teacher review.
Re-learn the skill with worked practice and clear examples.
Sort what changes, what is measured, what stays the same, and what comparison group is used.
| Question | Example |
|---|---|
| Independent variable | Temperature changed by the team |
| Dependent variable | Reaction time measured |
| Controlled variable | Same sample volume each trial |
| Control group | Room-temperature trial |
Use the variables table. In a fair enzyme test, pH is changed, reaction rate is measured, and sample volume stays 5 mL. Which is the controlled variable?
Reviewed| Question | Example |
|---|---|
| Independent variable | Temperature changed by the team |
| Dependent variable | Reaction time measured |
| Controlled variable | Same sample volume each trial |
| Control group | Room-temperature trial |
- A.pH
- B.The conclusion sentence
- C.Reaction rate
- D.Sample volume of 5 mL
Show the worked solution ▾
Answer: D. Sample volume of 5 mL
- Step 1: Look for what stays the same: The stem says sample volume stays 5 mL.
- Step 2: Match the term: A controlled variable is kept the same.
Why it's right: Sample volume is controlled because it stays the same.
- A: pH is changed on purpose.
- B: A sentence is not a variable.
- C: Reaction rate is measured.
Aligned to Biotechnology Research and Experiments · reading level ~grade 9
A team tests whether a hand sanitizer lowers bacterial growth. Half the agar plates get sanitizer and half get nothing at all. What is the half that gets nothing called?
Reviewed- A.The dependent variable, which is the amount of growth
- B.A second independent variable added to the test
- C.The control group, the plates left without sanitizer
- D.The controlled variable, since the plates are identical
Show the worked solution ▾
Answer: C. The control group, the plates left without sanitizer
- Step 1: Find the comparison: One set of plates gets the treatment and one set gets none.
- Step 2: Name the untreated set: The untreated set exists only so the treated set has something to be measured against, which makes it a control group.
Why it's right: A control group is a whole set of samples that receives no treatment, so any difference in growth can be traced to the sanitizer.
- A: The dependent variable is the growth you measure, not the plates you compare against.
- B: Only one factor is being changed here, so there is no second independent variable.
- D: A controlled variable is a condition held steady, like plate size, not a group of samples.
Aligned to Biotechnology Research and Experiments · reading level ~grade 9
- In Course Launch: Safety & Lab Foundations, this skill turns class evidence into a result another person can check.
Fill these in as you work through the lesson.
- Independent variable (what you change on purpose):
- Dependent variable (what you measure):
- Controlled variable (what stays the same):
- Control group (comparison without the tested change):
The independent variable is what you , the dependent variable is what you , and controls stay .
- What did the team change on purpose?
- What result did they measure?
- What stayed the same for a fair test?
A team changes temperature and measures enzyme rate while keeping pH the same. Label IV, DV, and one controlled variable.