Evaluation of Models and Experiments (ACT Science)

Understanding Scientific Models

A model is a simplified representation of a system or phenomenon used to:

• Explain observations
• Make predictions
• Test hypotheses
• Understand complex processes

Types of models on ACT:

• Physical models (diagrams, structures)
• Mathematical models (equations, graphs)
• Conceptual models (theories, frameworks)

Evaluating Models

Questions to Ask About Models

1. Does the model match the data?

• Compare model predictions to actual observations
• Look for agreement or discrepancies

2. What are the model's assumptions?

• What does it simplify or ignore?
• Are assumptions reasonable?

3. What are the model's limitations?

• Under what conditions does it work?
• Where does it break down?

4. Can it make testable predictions?

• Does it generate hypotheses?
• Can predictions be verified?

ACT Question Types

Type 1: "According to the model..."

Strategy:

• Find the relevant model (graph, diagram, equation)
• Read what it predicts for given conditions
• Don't overthink — answer is in the model

Type 2: "The model is supported by which observation?"

Strategy:

• Check each observation against model predictions
• Choose observation that matches/confirms model

Type 3: "Which result would contradict the model?"

Strategy:

• Understand what model predicts
• Find result that goes against that prediction

Understanding Experiments

Components of an Experiment

1. Hypothesis: Testable prediction

2. Variables:

• Independent variable: What experimenter changes
• Dependent variable: What's measured/observed
• Control variables: What's kept constant

3. Control group: Baseline for comparison

4. Experimental group: Receives treatment/manipulation

5. Procedure: Steps taken

6. Results: Data collected

7. Conclusion: What data shows about hypothesis

Experimental Design Principles

Control:

• Keep all variables constant except the one being tested
• Use control group for comparison

Randomization:

• Random assignment reduces bias
• Ensures groups are similar

Replication:

• Repeat trials for reliability
• Larger sample sizes are better

Precision:

• Use appropriate measuring tools
• Minimize measurement error

Evaluating Experiments

Quality of Experimental Design

Good experiments: ✓ Test one variable at a time
✓ Include adequate controls
✓ Have sufficient sample size
✓ Use precise measurements
✓ Can be replicated
✓ Minimize confounding variables

Poor experiments: ❌ Change multiple variables
❌ Lack proper controls
❌ Have too small sample size
❌ Use imprecise methods
❌ Can't be repeated

Interpreting Results

Questions to consider:

1. Do results support the hypothesis?

• Compare prediction to actual results
• Look for patterns in data

2. Are results consistent?

• Check for variability
• Look for outliers or anomalies

3. What can be concluded?

• State what data shows
• Avoid over-generalizing

4. What are alternative explanations?

• Could something else explain results?
• What other factors might be involved?

ACT Science Strategies

Strategy 1: Identify Variables

Always identify:

• What's being changed (independent)
• What's being measured (dependent)
• What's being controlled

Example passage might say: "Students tested how temperature affects reaction rate. They performed reactions at 20°C, 30°C, 40°C, and 50°C and measured time to completion."

• Independent: Temperature
• Dependent: Time to completion
• Controls: Amount of reactants, pressure, etc.

Strategy 2: Compare Experiments

When passage has multiple experiments:

• What's different between them?
• What's the same?
• What does each test?

Common pattern:

• Experiment 1: Tests variable A
• Experiment 2: Tests variable B
• Experiment 3: Tests variables A + B together

Strategy 3: Use Graphs and Tables

For model/experiment questions:

• Locate relevant graph or table
• Find the specific data point or trend
• Read directly from visual — no complex reasoning needed

Strategy 4: Evaluate Claims

"Which statement is supported by the data?"

Test each choice:

• Does data show this?
• Is there evidence for this claim?
• Or is this assumption/extrapolation?

Choose: Statement directly supported by results

Common Question Patterns

Pattern 1: Design Improvement

"How could the experiment be improved?"

Look for:

• Increasing sample size
• Adding control group
• Controlling additional variables
• Using more precise measurements
• Repeating trials

Pattern 2: New Hypothesis

"Based on these results, which hypothesis could be tested next?"

Strategy:

• Must relate to results
• Should extend/expand on findings
• Must be testable

Pattern 3: Model Prediction

"According to Model 1, what would happen if X increased?"

Strategy:

• Find trend in model
• Extend that trend to new condition
• No outside knowledge needed

Pattern 4: Comparing Models

"Models 1 and 2 agree that..."
"Models 1 and 2 differ in..."

Strategy:

• Check what each model says about the topic
• Find similarities (for "agree")
• Find differences (for "differ")

Common Mistakes

❌ Using outside knowledge instead of passage
ACT Science tests reading comprehension, not content knowledge

❌ Overthinking simple questions
Most answers are directly stated in graphs/tables

❌ Not identifying variables
Misunderstanding what's being tested leads to wrong answers

❌ Confusing correlation and causation
Data may show relationship without proving cause

❌ Ignoring control groups
Control is essential for valid conclusions

❌ Not reading axis labels
Graphs are useless if you don't know what they show!

Quick Tips

✓ Read the introduction — sets context for experiments/models
✓ Identify variables first — what changes, what's measured, what's constant
✓ Use process of elimination — often 2-3 choices clearly wrong
✓ Stick to the data — answer is in passage, not your head
✓ Check units — make sure you're reading right scale
✓ Look for trends — increasing, decreasing, or no relationship
✓ Compare controls — what's different tells you what's being tested

Practice Approach

1. Skim passage — identify type (experiment description, competing models, etc.)
2. Note variables — circle independent/dependent
3. Go to questions — read what they're asking
4. Find relevant data — locate graph, table, or description
5. Answer based on passage — not outside knowledge
6. Check reasonableness — does answer make sense?

Remember: ACT Science isn't a test of scientific knowledge — it's a test of your ability to read and interpret scientific information. Focus on understanding what's presented, not what you already know!