A hypothesis may be thought of as a well-informed guess that is drawn from a theory or collection of ideas. It provides the basis from which a reasoned prediction about the relationship between two or more factors is made (e.g., early attachment and the child's later educational attainment). The prediction should define clearly the factors and the group of people within which the relationship can be observed. After planning how best to control for the effect of the factors and assembling participants who reflect the defined group, scientific testing can proceed. The data gathered are then checked to see whether the hypothesis is supported or not.
Supporting data, however, cannot be taken as conclusive proof of the theory. Logically it is more persuasive to predict no relationship between two factors and then find through testing that there is a relationship. This is called the null hypothesis and is the theoretical basis for statistical examination of the data to test whether the relationship between the factors is greater than chance.
See also: METHODS OF STUDYING CHILDREN
Popper, Karl R. Conjectures and Refutations: The Growth of Scientific Knowledge. London: Routledge and Kegan Paul, 1963.