The Place of Hypothesis in Research

In view of the fact that a hypothesis is central to any scientific investigation, theoretical or experimental, it is necessary to study hypotheses in more detail. In this chapter, we will see, among other things, the “provisional” nature of hypotheses, meaning that there is nothing permanent, nothing final, about any hypothesis. But without hypotheses, there is no meaning, no pur­pose, to scientific investigation. Another way of saying this is that the hypothesis, the means, impels scientific investigation, the end. Like the propeller of a ship, which is hidden from view deep down but is nonetheless absolutely necessary for the ship to move, the hypothesis is essential, subtle, and not always obvious.

Its somewhat elusive nature makes it difficult to look at close up; that close-up look is attempted here.

There is a seeming exception to the above statement, namely, investigations in the classificatory sciences, like zoology and bot­any. Let us imagine that a botanist on his morning walk spots a particular plant, the like of which he has never seen before. His curiosity leads him to contemplate where, in his knowledge of classification, this new plant belongs. He considers, in order, to what family, genus, and species this plant should be assigned. And once that is done, his scientific curiosity takes a vacation until he reaches his home, lab, or library. If he is an active, curi­ous scientist—let us hope he is—he goes on to “confirm” his clas­sification. How does he do it? There are features—let us call them “properties”—common among all members of a family. He sets himself the task of studying the particular plant (or parts thereof), to see if this particular plant has the properties that characterize a family. If it does, he then feels elated and performs similar tasks at the next levels of genus, then species. At each level, when he is doing this task, he asks himself, for example, Could this be a member of species A? This is a hypothesis. Then, he does the investigation to compare the properties. If the answer is yes, he accepts this as confirmation of his hypothesis, and his investigation for the present ends there. If the answer is no, he comes up with another hypothesis: This particular plant is a member of species B. Again, the process of investigation begins and ends with a yes or a no, with confirmation or rejection of the hypothesis at hand.

This example is given here to stress that hypotheses are involved even in simple investigations. The above investigation is mostly theoretical in that—let us assume—our botanist is using only his library resources (including his own collection of speci­mens); that is, he is using already-known information.

Let us imagine a similar instance of a geologist finding a piece of rock, the like of which (geologically) he has never seen before. He then may require some tests to understand the rock’s physical properties and the reaction of some chemicals to it. Here again, the hypothesis is propelling him to do one test or another, but the nature of investigation here is “experimental,” though not completely so. Actually, the experiments he is doing are based on his knowledge of existing information about most other miner-als. In this case, the hypothesis is based on available “theory,” and he devises an experiment to confirm or reject his own hypothesis.

The sequence in the case of the botanist can be summed up as theory, hypothesis, confirmation or rejection. The sequence in the case of the geologist can be summed up as theory, hypothesis, experiment, confirmation or rejection. Thus, in the case of the geologist, the hypothesis involves the theory as well as the experiment.

Both the cases mentioned above involve what we may call pre­liminary hypotheses. It is often possible that some tests will be con­ducted to get a “feel” for the kind of question the investigator has in mind, when he is still uncertain about the right terms in which to form the question. Based on such a feel, the investigator may form a tentative hypothesis. This may happen more often with inventors, whose investigations are intended for patent rights, than with scientists, though in most cases, inventions are meant to be “answers” to specific gaps in knowledge. Thus, again, hypothesis leads to experimentation.

Let us imagine an investigator in the early days of electricity. Suppose he is “playing” with the measurement of current in sim­ple circuits, using a battery of known voltage across terminals of conductors. It is his purpose to discover which is the best con­ductor among four different metals, A, B, C, and D. But he faces a problem. His record (logbook) shows that on different days, he has used the same lengths of metal A, but he got different read­ings of current. He suspects that something is varying in those tests, which is causing the different currents. He now wants to do some controlled experiments. He measures the voltage every time the current is recorded; it does not vary. He double-checks the lengths of wires; they are constant within the accuracy of his measurement. He gets a clue that diameter may be the variable. He is now moving to another level of controlled testing. He keeps the voltage of the battery and the length of the wire A the same every time, but deliberately uses wires of different diameters and records the corresponding current readings. A tabular record shows that when thinner wires are used, the current readings are lower. At this stage he defines a new concept, resistance.

He is now in the situation where his guess has turned out to be correct. Reaching the next level of curiosity, he may think, I now know that smaller-diameter wires obtain less current; these offer greater resistance. But can there be a quantitative relation between the diameter of the wire and the resistance offered by the wire? Now he has reached the fourth level of his investigation rel­ative to the resistance of wires. This time, he selects wires of type A in several different diameters, controls the voltage and the lengths to remain the same, and gets several pairs of values of diameter against current. He states these values in a graph. He is pleased that the points have a trend close to a smooth curve, but he is a little disappointed that the relation is not a straight line.

The experimenter now feels puzzled and reflects, Suppose I consider the areas of the cross-section of the wires instead of the diameters. He does the necessary, simple calculations, plots another graph, this time plotting areas against current. He sees a straight line! He does not run naked in the street like Archimedes shouting, “I found it,” but he is very pleased with himself, as a scientist can be, though rarely.

This narration shows many iterations of experiments, from hypotheses to the final theory. To sum up the sequence:

Problem: With the same length wire A, why are there different currents?

• Hypothesis: There may be a variable; a closer look is necessary.

Experimental finding: With the same voltage and the same length of wire, the current is different for different diameters.

• Hypothesis: Wire diameter is a significant variable.

Experimental finding: Thinner wires offer more resistance.

This is a quantitative relation in terms of a concept newly defined, resistance.

• Hypothesis: Possibly there is a quantitative relation between wire diameter and resistance.

Experimental finding: The graphical relation between diameter and resistance is a smooth curve (good) but not a straight line (bad?).

• Hypothesis: The relation between resistance and the area of a cross-section of wire is more direct.

(Theory): (No experiment here; instead a theory involving some calculation is used.)

Confirmation: Resistance is inversely proportional to the area of cross-section.

The experimenter has, after all, used only wires of metal A. He now proceeds to the level of confirmation and speaks to him­self thus: If my (great) discovery is to be made public, I have to check it, using other metals as well. I shall do the last step of the experiment, namely, find resistance values for different diameters of wires of B, C, and D, plotting in each case resistance against the area of cross-section, to see if I can confirm a similar relation. This is hypothesis (v). So, now he performs his planned actions with anxiety. His theory passes the test: with confirmation, his hypothesis is now raised to the level of a theory.

The following points are significant to us in this narration:

1. A problem is the starting point of an investigation.
2. The problem is of interest—in fact, meaningful— only to those who are familiar with the back­ground from which the problem arises.
3. The hypothesis is a tentative answer to the prob­lem at hand (expressed in the form of an asser­tion).
4. The hypothesis must be confirmed or rejected based on experiment (or available information— the theory in the field).
5. The hypothesis precedes the experiment.
6. In some cases, experimental findings lead to better or different hypotheses.
7. There may be several iterations of the hypothesis- experiment phase.
8. The hypothesis, confirmed by experimental find­ings, becomes the theory.
9. A theory needs further confirmation; in this sense, the new theory takes the place of the hypothesis.
10. Based on this theory, now confirmed, further experiments or observations can be decided; these are often called crucial experiments (or tests).
11. If crucial experiments confirm the theory, it is established as a piece of scientific knowledge.

No theory, however well established, is the last word. If and when it fails to pass some test, either in a new experiment or implied by a new theory, it is open for reconsideration, modifica­tion, and even rejection.

Source: Srinagesh K (2005), The Principles of Experimental Research, Butterworth-Heinemann; 1st edition.