ACT Science — mixed practice, including what the measurement cannot settle

The other materials in this category take the three ACT Science formats one at a time. This one shuffles them, as the real section does, and is deliberately harder — not through vocabulary or outside knowledge, but through more steps between the numbers and the answer, options that sit closer together, and questions that ask what cannot be concluded.

Twelve questions across four scenarios: growth of a plant in four soils, a photosynthesis experiment, an extinction with two explanations, and two measurements weighed against the instruments that produced them. Every scenario is written out in full inside each question that uses it.

Four questions read data, and none of them is a single glance. The first asks which soil produced more than twice the height of the poorest, which means working out the threshold before looking at the list — and the second-tallest figure falls just short of it, so a reader who reaches for the runner-up instead of doing the arithmetic gets it wrong. Another offers four comparisons phrased identically, differing only in which two soils they name and in which order, so that recognizing a familiar-looking sentence is no help at all.

Four concern an experiment: which factor was varied, why one was held fixed, what the results do not establish, and what single change would let a factor that was held fixed be tested at last. The third of those is the one worth dwelling on. The experiment ran from 100 to 500 lux and the rate rose throughout; what it cannot say is what happens above 500, because a rate that climbs steadily across a tested range may keep climbing, level off, or fall away once some other limit binds.

Two concern a disagreement about why a bird died out, including what happens to each position when records turn up showing that its food supply never fell. The answer is carefully worded: the evidence weakens one account without confirming the other, and the difference between those two things is the whole question.

The last two are the hardest, and they combine a measurement with the instrument that made it. A rod that reads 2 millimeters longer on a ruler reliable to 2 millimeters has not been shown to have expanded. A pH that moves by 0.3 on a meter accurate to 0.5 has not been shown to have moved. Neither conclusion is refuted — they are simply not supported, and telling those apart is a habit worth more than any fact.

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• Switch between the three question formats and recognize which one you are looking at
• Work out a threshold or an intermediate value before comparing it against a list
• Answer a question that asks what CANNOT be concluded, rather than what can
• Refuse a conclusion about conditions outside the range that was actually tested
• Weigh a measured difference against the stated accuracy of the instrument that produced it
• Distinguish a conclusion that is refuted from one that is merely unsupported
• See that evidence weakening one explanation does not thereby confirm the other

Written as mixed practice across all three strands of the ACT science section — data representation, research summaries and conflicting viewpoints — following the skills the test's own published description names, with the addition of questions that weigh a measured difference against the precision of the instrument used. Every data set, experiment, dispute, species, site and instrument is invented for this material, and nothing is taken from any ACT publication or released test. There are no figures: each scenario is written out in words inside its own question and restated wherever it recurs. Metric units throughout.