Overview of the Process
Forming a good hypothesis is essential to the success of any science experiment. In order for a hypothesis to work well, it should be clear, testable, and express a relationship between something changed (the independent variable) with something that can be measured (the dependent variable). Even though the word guess is often used as a synonym for the word hypothesis, a hypothesis is not just a guess.
Making the Hypothesis Clear
A good hypothesis cannot be formed on the first try (like a first draft). When scientists have a research idea, it is the result of careful thought and observation about something in the world that can be stated in simple terms. For example, astronomers discovered several dwarf planets orbiting the Sun beyond Neptune, because they noticed that the motions of Uranus and Neptune were not quite what they expected. The simplest idea was that there was something causing the erratic motion.
Can It Be Tested?
A good hypothesis, if it is going to be useful, must be testable. This is especially clear with ideas in the field of social science. For example, some psychologists talk about unconscious impulses underlying much of behavior, but until there’s a way to measure and locate those impulses, it can’t be proven that they exist scientifically. (Nor can it be proven that they don’t exist, which is another point about ideas being testable.) If something cannot be proven nor disproven, it is often in the realm of philosophy.
Expressing Change Through Measurement: Growing Better Through Science
When conducting experiments, scientists manipulate one variable and measure what happens. That way, the hypothesis is both clear and testable. Whatever is manipulated or changed is called the independent variable, and what is measured is the dependent variable. The relationship between the change and the measurement of that change is the hypothesis. For example, suppose a researcher wants to know what fertilizer works best to grow plants. She devises a simple experiment, using three types of fertilizers (A, B, and C). The scientist chooses them and decides how they will be used, and they are the independent variable. In addition, the scientist measures growth by how tall the plant grows, and the measurement of length is the dependent variable.
Prediction, Prediction, Prediction
A good hypothesis also be stated as a prediction, a special kind of if-then statement which is clear, testable, and expresses relationships. For example, a scientist wants to determine the best time of day to feed lab rats. The hypothesis: If the time of day makes a difference, then the rats should eat a different amount of food when the time of day is changed. A lab technician in another part of the world should be able to repeat the experiment with their population of rats and get similar results.
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