GED Science Test: How to Read Graphs, Data & Experiments

The GED Science Test Is Not About Memorization

If you’re dreading the GED Science test because you think you need to memorize the periodic table or recite human anatomy, here’s the good news: the GED Science test is primarily a reasoning test. According to the GED Testing Service, the test focuses on your ability to understand scientific data, evaluate experimental designs, and draw evidence-based conclusions — not on rote memorization of scientific facts.

The test consists of approximately 34 questions to be completed in 90 minutes. Content is drawn from three domains: life science (40%), physical science (40%), and earth and space science (20%). Most questions are based on data presentations — graphs, tables, diagrams, and descriptions of experiments — that provide all the information you need to answer correctly.

This guide teaches you the core reasoning skills the test measures and gives you strategies for each question type. Want to see where you stand right now? Try our free GED Science practice test before you start studying.

How to Read Scientific Data

Data interpretation is the single most important skill on the GED Science test. Nearly every question involves reading information from a visual source. Here’s how to approach each type.

Bar Graphs and Line Graphs

Bar graphs compare discrete categories (e.g., population of different cities, yield of different crop varieties). When reading bar graphs:

Read the axis labels first — they tell you what’s being measured and in what units
Compare bar heights to identify the largest, smallest, and any patterns
Look for trends across categories (increasing, decreasing, or no pattern)

Line graphs show change over time or across a continuous variable. Key strategies:

Identify the overall trend — is the line going up, down, or staying flat?
Look for inflection points where the trend changes direction
Compare multiple lines on the same graph to find relationships
Pay attention to the scale — a steep-looking line on a compressed axis might represent a small actual change

Example question type: “Based on the graph, during which year did the population growth rate begin to decline?” Look for where the line’s slope changes from positive to less positive (or negative).

Data Tables

Tables present numerical data in rows and columns. To read them effectively:

Identify what each column and row represents
Look for the largest and smallest values
Calculate differences or ratios between values when the question requires comparison
Check units — mixing up milligrams and grams is a common error

Scatter Plots

Scatter plots show the relationship between two variables. Each point represents one observation. Look for:

Positive correlation: Points trend upward from left to right (as X increases, Y increases)
Negative correlation: Points trend downward (as X increases, Y decreases)
No correlation: Points are scattered randomly with no visible pattern
Outliers: Points that fall far from the general pattern — the test may ask you to identify these

Diagrams and Models

Scientific diagrams (cell structure, food webs, energy flow, rock cycle) require you to trace processes and relationships. The key is following the arrows or labels to understand the sequence of events or the direction of flow.

Understanding the Scientific Method

The GED frequently presents descriptions of experiments and asks you to evaluate them. Understanding the scientific method is essential.

Variables

Every experiment involves three types of variables:

Independent variable: What the researcher deliberately changes (also called the “manipulated variable”). Example: the amount of fertilizer applied to plants.
Dependent variable: What the researcher measures as a result (also called the “responding variable”). Example: the height of the plants.
Controlled variables: Everything the researcher keeps the same across all groups. Example: same soil type, same amount of water, same amount of sunlight.

Hypothesis and Prediction

A hypothesis is a testable explanation. The GED may ask you to identify which hypothesis an experiment is testing or to write a hypothesis based on experimental results. A good hypothesis follows the format: “If [independent variable changes], then [dependent variable will change] because [reasoning].”

Control Groups and Experimental Groups

The control group receives no treatment or the standard treatment — it serves as the baseline for comparison
The experimental group receives the treatment being tested

Example: To test whether a new fertilizer increases plant growth, the control group gets no fertilizer (or standard fertilizer), and the experimental group gets the new fertilizer. If the experimental plants grow taller, the difference is likely due to the fertilizer.

Drawing Valid Conclusions

A valid conclusion is directly supported by the data. Common errors on the GED:

Overgeneralization: The experiment tested one plant species, but the conclusion claims the result applies to all plants
Correlation vs. causation: Two variables change together, but that doesn’t prove one caused the other
Ignoring sample size: Results from 5 test subjects are less reliable than results from 500

Life Science Essentials

Life science covers approximately 40% of the GED Science test. You don’t need to memorize entire textbooks, but understanding these core concepts will help you interpret the passages and data you’ll encounter.

Cells and Cell Processes

All living things are made of cells. Key concepts:

Cell membrane controls what enters and exits the cell
Mitosis is cell division that produces two identical daughter cells — important for growth and repair
Photosynthesis converts light energy, water, and CO₂ into glucose and oxygen (plants)
Cellular respiration converts glucose and oxygen into energy (ATP), water, and CO₂ (all living things)

Genetics and Heredity

DNA carries genetic instructions in the form of genes
Dominant traits are expressed when at least one dominant allele is present (represented by capital letters)
Recessive traits are only expressed when two recessive alleles are present (represented by lowercase letters)
Punnett squares predict the probability of offspring inheriting specific traits — the GED may include these in data presentations

Example: If both parents carry one dominant allele (B) and one recessive allele (b), the Punnett square shows a 75% chance of the dominant trait and a 25% chance of the recessive trait in offspring.

Evolution and Natural Selection

Natural selection: Organisms with traits better suited to their environment are more likely to survive and reproduce
Adaptation: A trait that increases an organism’s fitness in its environment
Evidence for evolution: Fossil records, DNA comparisons, homologous structures (similar bone structures across species)

Ecosystems and Energy Flow

Energy flows through ecosystems in one direction: producers → primary consumers → secondary consumers → tertiary consumers
Food webs show the complex feeding relationships in an ecosystem
Decomposers break down dead organisms and recycle nutrients back into the ecosystem

Physical Science Essentials

Physical science also accounts for about 40% of the test. Focus on understanding the core principles rather than memorizing formulas.

Newton’s Laws of Motion

First Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion at the same speed and direction, unless acted on by an unbalanced force
Second Law: Force = mass × acceleration (F = ma). More force or less mass means more acceleration
Third Law: For every action, there is an equal and opposite reaction

Energy

Kinetic energy is the energy of motion
Potential energy is stored energy (gravitational, chemical, elastic)
Conservation of energy: Energy cannot be created or destroyed — it can only be converted from one form to another
Example: A roller coaster at the top of a hill has maximum potential energy and minimum kinetic energy. As it descends, potential energy converts to kinetic energy

Chemical Reactions

Reactants are the starting substances; products are the resulting substances
In a balanced equation, the number of atoms of each element is the same on both sides
Endothermic reactions absorb heat (feel cold); exothermic reactions release heat (feel hot)
pH scale: 0–6 is acidic, 7 is neutral, 8–14 is basic/alkaline

Earth and Space Science Quick Review

Earth and space science makes up about 20% of the test. Key topics:

Earth’s Systems

Plate tectonics: Earth’s crust is divided into plates that move slowly, causing earthquakes, volcanoes, and mountain formation at plate boundaries
Rock cycle: Igneous rock (from cooling magma) → sedimentary rock (from weathering and compaction) → metamorphic rock (from heat and pressure) → can become magma again
Water cycle: Evaporation → condensation → precipitation → collection → repeat

Weather and Climate

Weather is short-term atmospheric conditions; climate is the long-term pattern
Greenhouse effect: Certain gases (CO₂, methane, water vapor) trap heat in the atmosphere — this is natural, but increasing these gases intensifies the effect
The GED may present climate data and ask you to identify trends or evaluate claims about climate change

The Solar System

The eight planets orbit the Sun due to gravity
Inner planets (Mercury, Venus, Earth, Mars) are rocky; outer planets (Jupiter, Saturn, Uranus, Neptune) are gas/ice giants
Earth’s seasons are caused by the tilt of its axis (23.5°), not by distance from the Sun

Test-Taking Strategies

Read the Data Before the Questions

Unlike reading comprehension tests where you might skim first, science questions are data-dependent. Spend 30–60 seconds understanding the graph, table, or experiment description before reading the questions. Identify: What is being measured? What are the variables? What’s the overall trend?

Use the Process of Elimination

If you’re unsure of an answer, eliminate choices that contradict the data. Often, two answer choices can be ruled out quickly, leaving you with a 50/50 chance even if you’re unsure about the science content.

Don’t Bring Outside Knowledge You Don’t Need

The GED Science test provides all the information you need to answer each question within the passage and data. If an answer choice requires knowledge that isn’t in the passage and isn’t basic common knowledge, it’s probably wrong.

Watch for Qualifying Words

Words like “always,” “never,” “all,” and “none” in answer choices are usually wrong — very few things in science are absolute. Choices with “most,” “generally,” “often,” or “can” are more likely to be correct.

Manage Your Time

You have 90 minutes for approximately 34 questions — that’s about 2.5 minutes per question. If a question takes more than 3 minutes, flag it and move on. Return to flagged questions after completing the rest.

Ready to Practice?

Understanding scientific reasoning is a skill that improves with practice. Our free GED Science practice test includes 20 questions covering data interpretation, experimental design, and key science concepts. You’ll get instant feedback on your answers, helping you identify which areas need more study.

For a comprehensive study plan that covers all four GED subjects, check out our GED practice test study guide. And if you’re also preparing for the math section, our GED math formulas cheat sheet is an essential companion resource.