Science

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Test time: 90 min

Interpret experiments, data, charts, and scientific passages across life, physical, Earth, and space science.

Free sample lesson

Chapter 1: Scientific inquiry and experimental design (20 min)

Free sample lesson

Overview

Understand hypotheses, variables, controls, constants, samples, reliability, and validity.

Key concepts

• A hypothesis is testable; the independent variable changes and the dependent variable is measured.
• Controls provide a baseline, while constants prevent alternative explanations.
• Repeated trials, representative samples, precise measurement, and peer review strengthen evidence.

Method

1. Rewrite the question as “How does X affect Y?” to identify the variables.
2. Compare groups, find the control, and list what must stay constant.
3. Evaluate sample size, procedure, measurement error, confounding variables, and repeatability.

Worked example

In a light-and-growth test, light hours are independent and growth in centimeters is dependent; soil and water should stay constant.

Check yourself

• Was only one factor deliberately changed?
• Was the outcome measured objectively?
• Could another variable explain the result?

Practice

Design a fair test of how water temperature affects dissolving time.

More chapters — Premium

The remaining 6 chapters are part of the Premium course: