Read the data exactly

Lesson 5 · Science · about 9 minutes · fixes the data-reading slips behind 8 of your student's 13 Science misses on the 9/13 PreACT

Most of your student's Science misses were not about science. He knew enough; he read the wrong number: the wrong row, the wrong column, the wrong word, or the wrong power of ten.

ACT's own advice points the same way: "read the entire text and examine any tables, graphs, or figures associated with the question" (ACT Science tips). Its test description says the data questions measure "recognizing relationships among data in tables and graphs" (ACT Science test description). That is a reading skill, and reading skills can be drilled.

The method

Circle the exact quantity the question asks for, then find the column header and its units. "Change in length" is not "final length".
Scan every row before answering. The first plausible row is often a trap; the answer can sit in the last line.
Use the passage's own definitions. If the passage says "stiffness means X", reason with X, not with a word that sounds similar.
Check the direction of the trend in the table before accepting an explanation. Does the number actually go up when the claim says it goes up?
For units and equations, do the arithmetic, then sanity-check the size. Converting to a smaller unit gives a bigger number. In a balanced equation, the coefficients are the ratio.

A small made-up experiment

A student hangs a \(300\) g mass from four springs made of wires of different thickness. The passage defines stiffness as how hard a spring is to stretch: a stiffer spring stretches less under the same mass.

Table 1 (invented for this lesson)
Spring	Wire thickness (mm)	Starting length (cm)	Length with 300 g (cm)
A	0.6	8.0	15.1
B	1.0	10.0	14.6
C	0.8	12.0	17.5
D	0.5	15.0	22.8

Worked example 1 · scan every row

Which spring stretched the most?

Circle the quantity: "stretched" means the increase, final minus starting. No column gives it, so compute each row: A \(7.1\), B \(4.6\), C \(5.5\), D \(7.8\) cm.

Spring A's \(7.1\) jumps out first, and it is tempting to stop there. Spring D, in the last row, stretched more. Answer: D.

Worked example 2 · definition and trend direction

Which conclusion does Table 1 support? (a) Thicker wire makes a spring stiffer. (b) Thicker wire makes a spring less stiff.

Sort by thickness: D \(0.5\) → A \(0.6\) → C \(0.8\) → B \(1.0\) mm. The stretches go \(7.8\) → \(7.1\) → \(5.5\) → \(4.6\) cm: thicker wire, less stretch.

Now use the passage's definition: less stretch means stiffer. Answer: (a). The trap is to see "the numbers went down" and pick "less stiff" without translating through the definition.

Worked example 3 · units with powers of ten

Spring C stretched \(5.5\) cm, which is \(55\) mm. How many micrometers is that? (\(1\text{ mm}=10^3\ \mu\text{m}\))

\[55\times10^3=5.5\times10^1\times10^3=5.5\times10^4\ \mu\text{m}\]

Moving the decimal from \(55\) to \(5.5\) costs one power of ten, which must be added back. Sanity check: a micrometer is tiny, so the number must be big: \(55{,}000\). ✓

What to watch for with your student. Make him put his pencil on the column header and say the units out loud before he reads any number. When a question says "increase", "change" or "difference", he should write the subtraction on paper, not eyeball it. If he answers before his pencil has touched the last row, ask "did you check them all?"

Your turn

Questions 1–7 use this table. Question 8 is a quick equation check.

Table 2 (invented): seedlings grown for 14 days under five lamps
Lamp	Light (lux)	Starting height (mm)	Height on day 14 (mm)	Leaf area (cm²)
1	2,000	12	30	4.1
2	4,000	15	41	5.6
3	6,000	11	44	6.8
4	8,000	20	49	6.2
5	10,000	24	51	5.9