Research Summaries (ACT Science)

Experimental Design

Key Components

1. Independent Variable

• What the experimenter changes
• The cause in cause-and-effect
• Example: Temperature, time, amount of fertilizer

2. Dependent Variable

• What is measured or observed
• The effect in cause-and-effect
• Example: Plant growth, reaction rate, test score

3. Control Variables

• Factors kept constant
• Ensures fair test
• Example: Same soil type, same water amount

4. Control Group

• Does not receive the treatment
• Provides baseline for comparison
• Example: Plant with no fertilizer

5. Experimental Group

• Receives the treatment
• Compared to control group

Types of Experiments

Single Variable Experiments

• Change one independent variable
• Measure its effect on dependent variable
• Example: Test 3 temperatures, measure growth rate

Multiple Trial Experiments

• Repeat experiment several times
• Average results to reduce error
• Increases reliability

Common Question Types

Identifying Variables

"What was the independent variable in Experiment 2?"

• Look for what the researchers changed

"What was measured in this experiment?"

• The dependent variable

Understanding Purpose

"What was the purpose of using a control group?"

• To provide comparison/baseline

"Why did the researchers perform 3 trials?"

• To increase reliability/reduce error

Design Questions

"Which experiment would test the hypothesis?"

• Match the variables tested to the hypothesis

"How could the experiment be improved?"

• Add control group, more trials, control more variables

Reading Research Summaries

Passage Structure

1. Introduction: Background and hypothesis
2. Methods: What was done
3. Results: Data tables/graphs
4. Conclusion: What was learned (sometimes)

Strategy

1. Skim the introduction for context
2. Focus on methods - who did what?
3. Study the data carefully
4. Don't read every word - go to questions

ACT Tips

• Independent = what you change
• Dependent = what you measure
• Control = what stays the same
• Questions often test whether you understand why scientists made certain choices
• Use process of elimination on design questions