In this video, we're going to distinguish between predictions, hypotheses, and theories. A prediction is defined as an expected outcome of an event that can either be correct or incorrect. It addresses the answer to the question, What will happen? For example, I could make a prediction that tomorrow it will rain. Tomorrow, it will either rain or it will not, so my prediction of this expected outcome will either be correct or incorrect.
Now, the hypothesis is a bit different; it is defined as a proposed and testable explanation for an observation. The explanation here is very key. A well-designed hypothesis addresses the answers to two questions: What will happen, and why will it happen? The "why" is where the explanation plays a significant role. Since it answers the same question, "What will happen," as the prediction does, a good hypothesis will also include a prediction. For example, if we go back to the rain example, I could make a hypothesis that tomorrow it will rain because I pointed to the sky. A hypothesis might not always be true, but it will always be testable and include an explanation for both what will happen and why it will happen.
The last term, theory, is defined as a testable and broad hypothesis of many observations supported by a large body of evidence. The theory is, in many ways, similar to the hypothesis. It is distinguished by being broader, involving many observations, and supported by a substantial body of evidence. For example, with the rain scenario, a theory could state that every single time I point to the sky, it will rain the next day, explaining both why and what will happen on a much larger scale.
Below, we have another example applying the three terms prediction, hypothesis, and theory. Here on the left, we're starting the scientific method with an observation and a question. The observation is that the lawnmower won't start. A prediction could be that the lawnmower will start if you add gas. This prediction can either be correct or incorrect. A hypothesis might be that the lawnmower stopped working because it ran out of gas, so if you add gas, it will start working. This hypothesis answers both what will happen and why it will happen. A theory in this context would indicate that all lawnmowers stop working when they run out of gas and will start working when you add gas, applying this explanation to a broader range of observations.
It is essential to note that technically, hypotheses and theories can never be proven correct but can always be falsified, meaning they can be proven incorrect. This is why you must either accept or reject a hypothesis or a theory without claiming it to be true or correct. There are many theories in biology, and while they can be supported by many observations and substantial evidence, they can always be falsified or proven incorrect in the future. This concludes our lesson on distinguishing these three terms, predictions, hypotheses, and theories. Moving forward, we'll get a bit of practice, so I'll see you guys in our next video.