What is the main advantage of observational studies over experiments?

The advantage of observational studies over experiments is that in experiments, it cost much more time and money than observational studies for observational studies if faster to do and inexpensive. This is its advantage over the experiment, that is why other researchers prefer observational studies than conducting an experiment.

the relative standard reduction potential of the half-cell in which reduction occurs; more positive than the other half-cell. reduction is a chemical process in which electrons are added to an atom or an ion; it always occurs accompanied by oxidation of the reducing agent.

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