Textbook: psychology tenth edition in modules authored by david g. myers. Module 03: research strategies: how psychologists ask and answer questions. Theories lead to hypotheses which leads to research observations which can confirm, reject or revise our theory. Theory will be useful if it (1) organizes a range of self-reports and observations, and (2) implies predictions that anyone can use to check the theory or to derive practical applications. Theory: an explanation using an integrated set of principles that organizes observations and predicts behaviours or events. Hypothesis: a testable prediction often implied by a theory. Operational definition: a statement of the procedures (operations) used to define research variables. For example, human intelligence may be operationally defined as what an intelligence test measures. Replication: repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding extends to other participants and circumstances.