12.2 Graphs, Tables, and Scientific Models
Key Takeaways
- GED Science data questions require candidates to read axes, units, labels, table headings, and diagram keys before making a conclusion.
- A trend describes the pattern in the data, while a conclusion explains what the pattern supports or fails to support.
- Interpolation estimates between data points, but extrapolation extends beyond the data and should be treated with more caution.
- Scientific models are simplified representations that help explain relationships, but new evidence can support, limit, or weaken a model.
- Common GED Science calculations include averages, differences, rates, ratios, percent change, and substituting values into formulas provided in the item.
Start With the Display
GED Science questions often combine a short passage with a graph, table, diagram, map, or model. The official assessment targets include interpreting non-textual scientific presentations, reasoning from data, evaluating conclusions with evidence, and translating information from one form to another. That means the display is not decoration. It is usually the fastest path to the answer.
Before calculating, read the title, axis labels, units, legend, and table headings. A graph labeled dissolved oxygen in milligrams per liter is not showing temperature. A table that reports average values may support a different conclusion than a table that reports one trial. If the question asks for evidence, choose the data point or pattern that directly answers the claim.
Data Display Decision Table
| Display feature | What to ask | GED trap |
|---|---|---|
| X-axis | What condition or time is being compared? | Reading the wrong variable |
| Y-axis | What result is measured? | Ignoring units or scale breaks |
| Table heading | What does each column mean? | Comparing unlike quantities |
| Legend or key | Which line, symbol, or color matches the group? | Mixing up treatment and control |
| Trend | Does the value rise, fall, level off, or vary? | Treating one point as the whole pattern |
Trends, Predictions, and Conclusions
A trend is the pattern in the numbers. A conclusion is the claim supported by that pattern. For example, if seedling height increases from 4 cm to 9 cm to 13 cm as daily light increases from 4 hours to 8 hours to 12 hours, the trend is increasing height with more light. A supported conclusion is that, in this experiment, more daily light was associated with taller seedlings.
Be careful with prediction questions. Interpolation estimates within the tested range, such as predicting a value at 10 hours when the graph includes 8 and 12 hours. Extrapolation predicts beyond the tested range, such as 20 hours when the graph stops at 12. GED answers often reward the cautious statement: the data support a prediction within the tested range better than a claim far beyond it.
Scientific Models
A scientific model is a simplified representation of a system. Models can be diagrams, equations, food webs, particle drawings, climate maps, orbit diagrams, or cycle charts. A model is useful when it explains observations and makes reasonable predictions, but it is not the same as the real system.
When a GED item gives new evidence, ask whether the evidence supports, challenges, or limits the model. If a food web model shows insects as the only food source for a bird, but a field study finds the bird also eats seeds in winter, the model is incomplete. The new evidence does not prove the whole model is useless; it shows a needed revision.
Calculation Moves
GED Science does not expect you to memorize advanced formulas. Current official guidance says needed formulas or information are provided in the item, and an onscreen calculator is available. You still need to know what operation matches the data.
Use these common moves:
- Difference: final value - starting value.
- Mean: total of values / number of values.
- Rate: change / time.
- Ratio: one quantity compared with another.
- Percent change: change / original value * 100.
Evidence Test
After choosing an answer, point back to the exact number, graph pattern, or model feature that proves it. If you cannot identify that evidence, the answer may be based on background knowledge instead of the stimulus. GED Science rewards claims that stay inside the data.
A table shows average plant height after 14 days: 4 hours of light, 6 cm; 8 hours of light, 11 cm; 12 hours of light, 14 cm. Which conclusion is best supported?
A lake model predicts that dissolved oxygen drops when water temperature rises. New data show oxygen levels of 10 mg/L at 10 C, 8 mg/L at 15 C, 6 mg/L at 20 C, and 5 mg/L at 25 C. How do the data affect the model?