ACT Preparation / Unit 19 ACT 1824 review, 2 to 3 minutes
A Data Representation Passage
The idea
Data representation questions test reading, not recall. Read the title, the axes or headings, and the units first. Find values where a condition meets a measurement. Describe trends across the whole series, including peaks and leveling. Interpolate between measured points, and extrapolate beyond them only on the condition that the trend holds. Use differences, ratios and percents with friendly numbers, and carry values across figures through a shared quantity.
In practice
Worked passage, invented for the course: "Students grew radish seedlings under lamps of four brightness levels, 100, 200, 300 and 400 units, and measured average height after ten days: 2, 5, 7 and 7.5 centimeters. A second table gives leaf count by height: seedlings of 2 centimeters had 2 leaves, of 5 centimeters 4 leaves, and of 7 centimeters 6 leaves." Question one, the trend: height rises with brightness, quickly at first, then levels off between 300 and 400. Question two, interpolation: at 250 units, halfway between 200 and 300, height would be about halfway between 5 and 7, so 6 centimeters. Question three, arithmetic: from 100 to 200 units, height rose from 2 to 5 centimeters, an increase of 150%. Question four, two tables: at 300 units, height is 7 centimeters, and the second table gives 6 leaves for that height. Question five, extrapolation: at 500 units, the leveling suggests a height near 7.5 or a little more, not the 14 that a straight line through the first two points would give.
Where people slip
Three habits carry forward. Read units and scales before numbers. Describe a trend from the whole series, since many level off or turn. And state every extrapolation with its condition: if the trend continues. The next unit turns from reading data to judging how it was produced: experiments and their design.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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