Which of the following best defines a hypothesis?

• A. A guess without evidence.
• B. A routine measurement schedule.
• C. A testable prediction about a relationship between variables.
• D. A description of sensory observations.

Answer: (C)

A hypothesis is a testable prediction about how changing one factor will relate to another. It states what you expect to happen and how you will check it with evidence from experiments or observations. This makes it different from a routine schedule (which is about when you measure things) or a plain description of what you observe, and it’s stronger than a guess without a plan for testing. A good hypothesis specifies a relationship between variables, often identifying an independent variable you change and a dependent variable you measure, so you can determine whether the prediction holds. For example, if you increase sunlight for a plant, you might predict that its growth rate will increase; you can test that by giving different light levels and measuring growth. That description captures what a hypothesis really is, which is why it’s the best choice.