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Control Groups
“Without a suitable comparison, change can be mistaken for the passage of time or for expectation.”
01 / SUMMARY
In short
A control group provides a reference for estimating what would have happened without the intervention or under another condition. Its value depends on a relevant, well-maintained comparison.
03 / SCENE
In the wild
If both groups improve but treatment does no better than control, spontaneous recovery remains a plausible explanation.
04 / LIMIT
The limit
Control does not always mean doing nothing; it may be placebo, usual practice, or another intervention.
FINAL NOTE
What remains
Ask which counterfactual the comparison group is meant to represent.