Choose the comparison
Read the study brief. Check what changes, who is randomized, and what carries into the next period.
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Match two characteristics before randomizing within each pair.
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6 questions · No time limit
Example
Example
Example · Standard
Packing task. Pair volunteers who match on both Site and Experience, then randomize within each pair. Which plan matches everyone correctly?
| Person | Site | Experience | Session |
|---|---|---|---|
| A | North | New | Early |
| B | North | Practiced | Late |
| C | South | Practiced | Early |
| D | North | New | Late |
| E | South | New | Early |
| F | North | Practiced | Early |
| G | South | Practiced | Late |
| H | South | New | Late |
| Plan | Pairs |
|---|---|
| Plan A | A + F · E + C · H + G · D + B |
| Plan B | A + D · E + H · C + G · F + B |
| Plan C | F + C · D + H · A + E · B + G |
- Questions answered
- 0 / 6
- Active time
- 0:00
Ready to start?
Choose the plan that meets every stated condition.
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Reload pageOptional and off by default. Share starts, completions, replays and error categories. For visits from ChatGPT, starts and completions can also include the first QuickenBrain page and broad country. No answers, drawings or names.
How this data is usedHelp
Compare study designs under explicit assumptions. Random assignment helps estimate an effect but does not guarantee perfect balance or remove every source of bias. Matching, allocation units and carryover address different problems. These are original reasoning exercises, not a validated intelligence assessment.
Each round has six questions and no time limit. Choosing an answer locks it. Review the steps, then move to the next question. Finish all six to save the round. Active time includes reviewing the steps, but does not count time when this page is hidden. Speed does not affect your score.
Use Tab and Enter or Space to choose an answer. The number keys also select answers, except when another control is focused. After an answer, Enter goes to the next question.
Original practice puzzles, not a standardized assessment.
About this practice
Learn a method
Isolate the changing conditionRead the study brief. Check what changes, who is randomized, and what carries into the next period.
Report a problem
Optional and off by default. Share starts, completions, replays and error categories. For visits from ChatGPT, starts and completions can also include the first QuickenBrain page and broad country. No answers, drawings or names.
How this data is used