In the first example, the extra number of cases per thousand people is
A headline announces that eating a certain food raises the risk of a disease by fifty per cent. The figure sounds alarming, but on its own it tells us very little. If the disease affects two people in a thousand, a fifty per cent rise takes it to three in a thousand: one extra case for every thousand people. If it affects two in ten, the same rise means an extra one in ten. The relative change is the same; the absolute change is entirely different. Reports that give only the relative figure exaggerate small risks and are easy to produce, because the figure is always larger than the absolute one when the baseline risk is low. A responsible report gives both, and says who was studied.
Answer and explanation
Correct answer: E. one
- Step 1: Two in a thousand rising by fifty per cent gives three in a thousand.
- Step 2: Three minus two leaves one extra case per thousand.
Answer
one.
Why not the others: Two is the baseline, three is the new total, and fifty is the percentage rise.
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