Change one, keep the rest the same
Two puris fry side by side, test A and test B. B has hotter oil and thinner dough. B is faster. Why?
Step 1 of 4
- Test A and test B, side by side.
- A fair pair changes only the oil heat: cooler, then hotter.
- Thickness, flour and how the dough goes into the oil stay the same.
- One thing differs, so it is the cause you test.
In the first pair, two things differ. So either one could be the reason.
The rule
Change one thing and keep the rest the same. Then the changed thing is the one cause you are testing. Change two things and you cannot tell which caused it. Change nothing and nothing is tested.
Two switches change test B. Try one, then both.
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