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Predictions and Experiments

A corroborated hypothesis is one that has passed its tests (i.e. one whose predictions have been verified). Consequently different scientists test the hypothesis. If further corroborated by subsequent tests, it becomes highly corroborated and is considered to become reliable knowledge. The technical name for this part of the scientific method is the “hypothetico-deductive method”.

The hypothetico-deductive method is named because one deduces the results of the predictions of the hypothesis and tests these deductions. Inductive reasoning, the alternative to deductive reasoning, was used earlier to help formulate the hypothesis. Both these types of reasoning are therefore used in science, and both must be used logically.

Karl Popper
Karl Popper

If the predictions are not accessible by observation or experience, the hypothesis is not yet useful, and must wait for others who might come afterward, and perhaps rekindle its line of reasoning, for instance, a new technology or theory might make the necessary experiments feasible.

Once predictions are made, they can be tested by experiments. If test results contradict predictions, then the hypotheses are called into question and explanations may be sought. Sometimes experiments are conducted incorrectly and are at fault. If the results confirm the predictions, then the hypotheses are considered likely to be correct but might still be wrong and are subject to further testing.

It is essential that the outcome be currently unknown. Only in this case does the eventuation increase the probability that the hypothesis be true. If the outcome is already known, it’s called a consequence and should have already been considered while formulating the hypothesis.

A useful hypothesis will enable predictions, by reasoning including deductive reasoning. It might predict the outcome of an experiment in a laboratory setting or the observation of a phenomenon in nature. The prediction can also be statistical and only talk about probabilities.

Every hypothesis has consequences and makes certain predictions about the phenomenon or process under investigation. Using logic and empirical evidence, one can test the hypothesis by examining how successful the predictions are, that is, how well the predictions and consequences agree with new data, further insights, new patterns, and with models.

The testability or predictiveness of a hypothesis is its most important characteristic. A hypothesis must be tested before it is corroborated and attributed any real validity. There are two ways to do this. First, one can conduct an experiment. This is often presented in science textbooks as the way to test hypotheses in science. The second way to test a hypothesis is to make further observations.

observations

The problem is that parts of the theory itself need to be assumed in order to select and report the experimental conditions. The observations are sometimes hence described as being ‘theory laden’. Theory laden refers to the property of observations varying with or depending upon the theoretical commitments of the observer. To the extent that observations are theory laden, belief’s – as shaped by the theory or paradigm one accepts – determine what one observes, so that partisans of different theories (or paradigms) will observe differently.

Scientists assume an attitude of openness and accountability on the part of those conducting an experiment. Detailed record keeping is essential, to aid in recording and reporting on the experimental results, and providing evidence of the effectiveness and integrity of the procedure. They will also assist in reproducing the experimental results.

In every experimental science “experience is supreme” and experimental verification of hypothetical predictions is absolutely necessary. Experiments may test the theory directly or may test for consequences derived from the theory using mathematics and logic. The necessity of experiment implies that a theory must be testable.

It is not possible for a scientist to record everything that took place in an experiment. They must select the facts that they believe to be relevant to the experiment and report them. This may lead, unavoidably, to problems later if some supposedly irrelevant feature is questioned. For example, Heinrich Hertz did not report the size of the room used to test Maxwell’s equations, which later turned out to account for a small deviation in the results.

Often the experiment is not done by the person who made the prediction and the characterization is based on experiments done by someone else. Published results of experiments can also serve as a hypothesis predicting their own reproducibility. Crucially, experimental and theoretical results must be reproducible by others within the science community.

Frequently the scientific method is not employed by a single person, but by several people cooperating directly or indirectly. Such cooperation can be regarded as one of the defining elements of a scientific community. Various techniques have been developed to ensure the integrity of the scientific method within such an environment.

Experimental tests may contribute either to the confirmation of the hypothesis, or to the ruling out of the hypothesis. The scientific method requires that an hypothesis be ruled out or modified if its predictions are clearly and repeatedly incompatible with experimental tests. No matter how elegant a theory is, its predictions must agree with experimental results if we are to believe that it is a valid description of nature.

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