A hypothesis is a set of beliefs about the nature of the world, usually concerning the relationship between two or more variables. Hypothesis testing is the scientific method of collecting observations to confirm or disconfirm beliefs about the relationships among variables. Inadvertently, we may act in ways that will lead us to confirm or disconfirm hypotheses according to our expectations. These are called self-fulfilling prophecies. When we draw conclusions from observations, it s important to utilize an adequately large sample size because people are variable in the way they respond.
Most people are too willing to generalize results obtained from small samples.
In everyday context, we often use retrospective techniques to understand what caused an event to occur. This is not a good technique because our memories tend to be selective and malleable and because we have no objective systematic observations of the cause. Prospective techniques that record events when they occur and then see if the hypothesized result follows are better methods for determining cause-effect relationships. Correlation Does Not Imply Causation Variables that are related so that changes in one variable are associated with changes in the other variable are called correlated variables. The deliberate use of emotional and nonemotional words is designed to influence how one thinks about a topic.