Some good hypothesis examples include, "When there is less oxygen in the water, rainbow trout suffer more lice" and, "Aphid-infested plants exposed to ladybugs have fewer aphids after a week than untreated plants." Effective hypotheses are simple enough to be testable, but not so simple that they are common knowledge.
Strong hypotheses are most often written in the, "If A occurs, then B will occur" format and are presented as statements, not questions. Good hypotheses also are clear and keep variables in mind, defining them in easy-to-measure terms. Key features of a good hypothesis are that it is testable, researchable and simple enough to be tested with one or two experiments.