ACT Preparation / Unit 20 ACT 1926 worked example, 60 to 90 seconds
Modifying an Experiment
The idea
A question about how to test a new idea is answered in three steps. First, state the new question as a factor and a result: does this factor change that result? Second, make that factor the only independent variable, keeping every other condition as in the original. Third, keep or add a control group for comparison, and choose the design that changes nothing else.
In practice
Worked example: after the bean study, a student wonders whether the amount of water matters. The modified experiment keeps every pot under the same white light and gives different pots 50, 100 and 150 milliliters of water a day, measuring stem height. A design that also varies the light color answers neither question.
Where people slip
The best modification is the smallest change that isolates the new factor.
Your place on the trail
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Unlocks
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