12.2 Graphs, Tables, and Scientific Models

Start With the Display, Not the Options

A large share of GED Science items pair a short passage with a graph, table, diagram, map, or model. The assessment targets explicitly include interpreting non-textual presentations, reasoning from data, evaluating conclusions against evidence, and translating information from one form to another (for example, reading a value off a graph and re-stating it in a sentence). Treat the display as the engine of the question, not decoration.

Before you calculate, read the title, axis labels, units, legend, and table headings. A graph labeled "dissolved oxygen (mg/L)" is not showing temperature, even if temperature sits on the x-axis. A table of average values may support a different claim than a table reporting a single trial. When a question asks for the evidence behind a claim, point to the exact data point or pattern that answers it, and ignore the impressive-sounding choices that the numbers do not support.

Data-Display Decision Table

Trends, Predictions, and Conclusions

A trend is the pattern in the numbers; a conclusion is the claim that pattern supports. If seedling height rises from 4 cm to 9 cm to 13 cm as daily light goes from 4 to 8 to 12 hours, the trend is increasing height with more light, and the supported conclusion is that, in this experiment, more light was associated with taller seedlings.

Prediction questions hinge on a single distinction. Interpolation estimates within the tested range (a value at 10 hours when the graph shows 8 and 12). Extrapolation projects beyond it (20 hours when data stop at 12). GED answers reward the cautious statement: a within-range prediction is far safer than a far-beyond claim, because nothing in the data guarantees the trend continues.

Scientific Models

A scientific model is a simplified representation of a system: a diagram, an equation, a food web, a particle drawing, an orbit diagram, or a cycle chart. A model is useful when it explains observations and makes reasonable predictions, but it is never identical to the real system. When an item supplies new evidence, ask whether the evidence supports, challenges, or limits the model. If a food-web model lists insects as a bird's only food, but a winter field study finds the bird also eats seeds, the model is incomplete, not worthless; the correct answer calls for a revision, not a rejection.

Calculation Moves (Calculator Provided)

GED Science does not require you to memorize advanced formulas: official guidance states that any needed formula or information is given in the item, and an on-screen TI-30XS calculator is available on most questions. Your job is to match the operation to the data:

• Difference = final value - starting value
• Mean (average) = sum of values / number of values
• Rate = change / time
• Ratio = one quantity compared with another (a : b)
• Percent change = (change / original value) x 100

The Evidence Test

After selecting an answer, force yourself to name the exact number, graph segment, or model feature that proves it. If you cannot point to that evidence in the stimulus, your answer is probably leaning on outside background knowledge, which is exactly where GED Science wrong-answer traps live. The discipline that wins points is staying inside the data and choosing the claim the evidence can actually carry.

Reading Tricky Displays

GED graph items hide points inside the layout. Watch for a broken y-axis (a zig-zag near the origin) that exaggerates small differences, a double y-axis where two lines use different scales, and bar vs. line choices (bars compare categories, lines show change over a continuous variable like time). On a scatterplot, a positive correlation rises left to right, a negative correlation falls, and a cloud with no slope shows no relationship. When two variables both rise, remember correlation is still not causation; the safe answer states an association.

A Worked Percent-Change Item

Suppose a table shows a bacteria count of 200 cells at hour 0 and 320 cells at hour 4, and the item asks for the percent increase. Apply the five operations above: the change is 320 - 200 = 120 cells; divide by the original 200, not the final 320, to get 120 / 200 = 0.6; multiply by 100 for a 60 percent increase. Dividing by 320 (the final value) yields a wrong 37.5 percent, which is the planted distractor. Always anchor percent change to the starting value, and label the answer as a percent, not as cells.