Comment In experiments, correlation implies causation (Score 1) 223
Data arises from retrospective or prospective studies.
Retrospective data was created before a statistician could design an experiment.
Prospective data sees the statistician set various levels of a variable
to randomly selected experimental units (maybe people, maybe production machines).
In a (prospective) experiment, an observed correlation implies causation.
For example, in manufacturing plastic, keeping constant other variables (humidity and speed of production),
set the temperature sometimes at 100 degrees and sometimes at 200 degrees,
randomly choosing the order these temperatures get applied.
If the 200 degree temperature produces a stronger plastic (response or dependent variable),
then your positive correlation implies causation.
In the future, knowing that increased heat increases plastic strength, the manufacturer would raise the temperature.
But experiments consume time and money, so institutions not individuals usually perform them.
Million dollar clinical trials do determine whether a drug is effective.
While experimental economics can determine causation, most economics is retrospective, so conclusions become controversial.