Predictions can be made about the observations that would be expected. These predictions allow the scientist to formulate an experimental design and a plan for measuring the observations. Ingestion of alcohol causes a decline in fine motor skills. Ingestion of alcohol causes moral decay. An active volcano can be prevented from erupting by throwing a virgin into it once a month.
Prayer can increase rates of recovery from cancer.
The earth and all its creatures were created by an all-powerful, unknowable being. Cigarette smoking is an addictive behavior. Testing hypotheses is best done by experimentation, that is designing experiments or a series of observations to be made. In some cases experimentation is not possible for practical or ethical reasons. The problem with not testing hypotheses experimentally is that factors can be associated, or correlated, with each other without having a causative relationship.