ACT Preparation / Unit 20 ACT 1905 worked example, 60 to 90 seconds
Which Hypothesis Was Tested?
The idea
A question about what an experiment tested is answered in three steps. First, find what the researchers changed on purpose between groups or trials. Second, find what they measured. Third, choose the hypothesis that links the changed factor to the measured result, and reject hypotheses about factors that were never varied.
In practice
Worked example: in an invented study, students grew beans in identical pots under red, blue and white light, and measured stem height after two weeks. Changed: light color. Measured: stem height. The hypothesis tested is that light color affects bean stem growth. A hypothesis about the amount of water was not tested, because every pot received the same water.
Where people slip
A study can mention many factors in its setup. Only the factor varied on purpose is under test, and a factor held the same in every trial can tell you nothing about its own effect.
Your place on the trail
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