An experiment is always conducted to test your hypothesis. To find out which experiment you should conduct you look at what your question states. Whatever you question states is what you are testing.

Ex: What will happen if you mix sugar with water?

Hypothesis: If I mix salt with water then the sugar will dissolve.

You would conduct your experiment based on the question, "what will happen if you mix sugar with water," so you would mix sugar with water to find out if your hypothesis is correct or incorrect.