John Hay
John Hay Biomedical
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Principles of Biomedical Technology (Principles of Biomedical Science)
Unit 0: Course Launch: Safety & Lab FoundationsPBS LaunchBiotechnology Research and Experiments

Identify Variables and Controls

Sort what changes, what is measured, what stays the same, and what comparison group is used.

Builds on (2 levels back)inferred · high confidence
  • 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.

Step 1: Learn the key
The independent variable is what you [blank], the dependent variable is what you [blank], and controls stay [blank].
QuestionExample
Independent variableTemperature changed by the team
Dependent variableReaction time measured
Controlled variableSame sample volume each trial
Control groupRoom-temperature trial
Variables and controls table
Step 2: Use the model
Read the figure, table, control, range, or protocol before choosing an answer.
Step 3: Name the limit
Say what the evidence can support and what it cannot prove yet.
Practice

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
QuestionExample
Independent variableTemperature changed by the team
Dependent variableReaction time measured
Controlled variableSame sample volume each trial
Control groupRoom-temperature trial
Variables and controls table
  1. A.pH
  2. B.Reaction rate
  3. C.Sample volume of 5 mL
  4. D.The conclusion sentence
Show the worked solution ▾

Answer: C. Sample volume of 5 mL

  1. Step 1: Look for what stays the same: The stem says sample volume stays 5 mL.
  2. 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.

Why the others miss:
  • A: pH is changed on purpose.
  • B: Reaction rate is measured.
  • D: A sentence is not a variable.

Aligned to Biotechnology Research and Experiments · reading level ~grade 9

Where you'd see this
  • In Course Launch: Safety & Lab Foundations, this skill turns class evidence into a result another person can check.
Careers that use this
Biomedical Data Analyst: Uses identify variables and controls to make a decision from evidence without overclaiming.
Video library
Watch: Identify Variables and Controls
Nature of Science
Amoeba Sisters
Guided notes

Fill these in as you work through the lesson.

Big idea: Sort what changes, what is measured, what stays the same, and what comparison group is used.
Key terms: write the meaning
  • 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 rule

The independent variable is what you  , the dependent variable is what you  , and controls stay  .

Check yourself
  1. What did the team change on purpose? 
  2. What result did they measure? 
  3. What stayed the same for a fair test? 
Work one example

A team changes temperature and measures enzyme rate while keeping pH the same. Label IV, DV, and one controlled variable.