GED Science
Interpreting Scientific Data
Data questions hand you a table or graph and ask what it shows. The whole skill is reading the axes first, tracing the trend, and then refusing to claim more than the picture proves — especially refusing to turn "these move together" into "one causes the other."
The words first
- axes
- x (bottom) = what was varied; y (side) = what was measured
- trend
- the overall direction: rising, falling, flat, or leveling off
- correlation vs causation
- moving together vs one driving the other — the test's favorite trap
- outlier
- one point far off the pattern — note it, don't let it rename the trend
- extrapolate
- extend the trend past the data — always uncertain
The method
THE READING ORDER (30 seconds, always)
1. Title — what was studied?
2. x-axis label and units — what did they vary?
3. y-axis label and units — what did they measure?
4. NOW look at the shape:
rising / falling / flat / leveling off / peak
SAYING ONLY WHAT THE PICTURE PROVES
data: ice-cream sales and drownings both rise in July
✓ "the two rise together" (correlation)
✗ "ice cream causes drowning" (causation — unearned)
likely: a third factor (summer heat) drives both
READING BETWEEN AND BEYOND POINTS
between measured points → interpolation, fairly safe
beyond the last point → extrapolation, say "about" and
trust it less the farther you go
Worked all the way through
The problem
A graph shows plant height (y, cm) against daily water (x, mL). Height rises steeply to 40 mL, then the line goes flat through 80 mL. What does the graph show, and what should a gardener do?
- Step 1 — Read the axes.They varied daily water; they measured height.
- Step 2 — Describe the shape in two pieces.Rising from 0 to 40 mL: more water, taller plants. Flat from 40 to 80: extra water adds nothing.
- Step 3 — Name the pattern.A leveling-off — benefit up to a threshold, then a plateau.
- Step 4 — Turn it into advice without exceeding the data.Water about 40 mL; more is wasted. (The graph doesn't show HARM above 80 — don't claim it.)
On the board
x: water (mL) · y: height (cm)
axes first
0→40 mL: line climbs
more water → taller
40→80 mL: line flat
no added benefit
pattern: levels off at 40
advice: ~40 mL, more is waste
claim only what's shown
Answer
Height increases with water up to about 40 mL, then levels off — water roughly 40 mL
A second one, in a different form
A study finds neighborhoods with more libraries have less crime. A headline says "Libraries reduce crime." What's the flaw?
the data: two things move together
correlation
headline claims one causes the other
causation
a third factor could drive both
wealth, city investment
the data can't pick between stories
Answer
It turns a correlation into causation — richer areas may fund both libraries and safety
The usual mistake
Accepting a causal claim because the relationship sounds sensible.
Check yourself
Spend the first 30 seconds on the title and both axis labels before looking at any line. And before choosing any answer with "causes" in it, ask whether the study CHANGED something or merely OBSERVED it — observation alone never earns "causes".
Practice it
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