3.1 Science Data and Experiments

Science Is Evidence First

The GED Science test gives you enough information in each passage, table, diagram, or experiment to reason your way to the answer. You still need core vocabulary, but the higher-yield skill is deciding what the evidence actually shows. The test runs 90 minutes with no break and is organized around three science practices: reading for meaning in science, designing and interpreting science experiments, and using numbers and graphics in science.

A calculator (the on-screen TI-30XS) and a calculator/formula reference sheet are provided, so your attention should stay on setup, interpretation, units, and claim strength rather than on memorizing equations. Items appear as multiple choice, drag-and-drop, fill-in-the-blank, drop-down, and hot-spot. Treat every item as a small evidence task: figure out the question first, then mine the stimulus.

The content blueprint is roughly 40% life science, 40% physical science, and 20% Earth and space science — so the bulk of the test sits in biology and physical science, not astronomy.

Experiment Setup

Almost every experiment question turns on separating four roles. Tag them before reading the choices.

Use this routine on experiment items:

1. Name the measured outcome before reading any choice.
2. Identify the single condition that differs between groups.
3. Confirm all other conditions were held constant.
4. Compare each treatment group against the control.
5. Pick the conclusion that is no stronger than the evidence.

Reading Data Displays

Start with the title, axis labels, and units — not the numbers. A line graph usually shows change over time; a bar graph compares categories; a table may require sorting, subtracting, or computing a rate. If the item asks for a trend, do not over-weight one unusual point unless the question is about that point.

Worked example: a table shows mean plant height at fertilizer doses of 0, 25, 50, and 75 grams reading 4 cm, 9 cm, 12 cm, and 8 cm. Growth rises then falls. The supported conclusion is that growth increases up to about 50 g and then declines — not that "more fertilizer always helps." The drop at 75 g is the data point that kills the more-is-better answer.

Correlation, Causation, and Claim Strength

Correlation means two measurements move together. Causation means one factor produces the change in the other. The GED repeatedly tests whether you will overclaim causation from observational data. A graph showing asthma visits and air-pollution levels rising together shows a relationship; only a controlled study with comparable groups and a control supports a cause.

Strong answers use careful verbs: supported, suggests, consistent with, likely under these conditions. Weak answers say proved, always, never, caused when the design cannot justify that certainty. Flag designs that lack a control group, lack random assignment, use a tiny sample, or change two factors at once.

Content Areas to Recognize

• Life science (~40%): cells, human body systems, genetics and heredity, evolution and natural selection, ecosystems, energy flow, photosynthesis and cellular respiration.
• Physical science (~40%): matter and its properties, chemical vs. physical changes, force and motion (net force), waves, electricity, heat, and conservation of energy.
• Earth and space science (~20%): plate tectonics, Earth systems and cycles, weather vs. climate, natural resources, the solar system and universe.

You do not need a textbook in your head — you need to link vocabulary to evidence. Producers make energy available in food chains. Net force explains changes in motion. Plate boundaries explain earthquakes, volcanoes, and mountain building. A physical change keeps the same substance; a chemical change forms a new one. These anchors let you read the stimulus faster.

Numbers and Graphics in Science

The "using numbers and graphics" practice means basic statistics applied to science data. Know these by heart: the mean is the sum divided by the count; the median is the middle value when sorted; the range is highest minus lowest; a rate is one quantity per unit of another (such as cm per week). Worked example: if five trials yield reaction times of 2, 4, 4, 6, and 9 seconds, the mean is 25 / 5 = 5 s, the median is 4 s, and the range is 9 - 2 = 7 s. A single slow trial pulled the mean above the median — a clue that the data is skewed by an outlier.

Scientific notation and unit conversion show up too. Reading 3.0 x 10^8 m/s correctly, or converting grams to kilograms, can decide an item. Use the on-screen calculator and the reference sheet rather than guessing, and confirm the units in the answer match the units in the question.

Final Science Checklist

• Identify the changed factor and the measured result.
• Use the control group as the baseline comparison.
• Read units and axis direction before any calculation.
• Separate data-supported claims from guesses.
• Watch correlation being overstated as causation.
• Compute mean, median, and range carefully when asked.
• Prefer the answer that fits all the data, not one point.

Slow down at the start of each stimulus. A few seconds spent labeling variables and units usually saves more time than diving straight into the choices, and it keeps you from being fooled by a single outlier or a choice that overstates the strength of the result.