Question

How can an experiment show cause and effect?

Answer 1

An experiment can not prove a cause and effect relationship. However, given a "cause and effect" hypothesis, an experiment can demonstrate results consistent with the hypothesis.

Explanation:

Repeated experiments which produce results consistent with a cause-effect relationship provide evidence to support the relation hypothesis.

Alternately an experiment can be used to disprove a cause-effect hypothesis. It only requires one counter example to disprove a hypothesis.

Causality is a difficult concept to define (and even more difficult to prove).