ACT Preparation / Unit 20 ACT 1912 worked example, 60 to 90 seconds
Finding the Control
The idea
A control question is answered in three steps. First, list the groups or trials and what each received. Second, find the one that received no treatment, or the standard condition the others are compared against. Third, check that it differs from the others only in the treatment; if it differs in anything else, it is a flawed control.
In practice
Worked example: an invented study tests whether a fertilizer increases tomato yield. Plot A gets the fertilizer, plot B gets twice as much, and plot C gets none, and all three get the same soil, sun and water. Plot C is the control: the same conditions, with no fertilizer. Had plot C also been in shade, it would differ in two ways, and the comparison would be unfair.
Where people slip
A study can compare treatments without a control, as plots A and B alone would; then it can show which dose did better, but not whether fertilizer helps at all.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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