Less demanding than the task of creating a new theory is that of revising an existing theory so as to provide either a more satisfactory classification system or a more adequate explanation of phenomena.

Revising a classification system usually consists of (a) adding new classes, (b) dividing existing classes into more precise subtypes, or (c) rearranging the hierarchy of classes so that major and minor categories assume a different pattern.Revising an explanatory theory can involve any one or more of the following adjustments: (a) adding new causal factors, (b) dividing existing causal factors into more precise components, (c) proposing a different weighting of factors (assigning more importance or power to certain factors and reducing the significance or strength of others in their influence on the outcome variable), and (d) describing a different pattern of interaction than the pattern proposed in the original theory.A further way to adapt an explanatory theory is to accept the original author's factors and mode of interaction, but to devise different techniques for appraising the factors and their interactions than those used in the original version. For instance, you might substitute an interview system for the original author's questionnaire approach to data collection. Or you might create a rating scale for recording observations of people's behavior rather than depending on the original author's method of using people's self-reports.

PLANNING CHECKLIST

Completing the following checklist may help you identify the roles that you will assign to classificatory and explanatory theories in your project.