After studying Chapter 2, you should know and understand the following key points:

Scientific and Everyday Approaches to Knowledge

The scientific method is empirical and requires systematic, controlled observation.

Scientists gain the greatest control when they conduct an experiment; in an experiment, researchers manipulate independent variables to determine their effect on behavior.

Dependent variables are measures of behavior used to assess the effects of independent variables.

Scientific reporting is unbiased and objective; clear communication of constructs occurs when operational definitions are used.

Scientific instruments are accurate and precise; physical and psychological measurement should be valid and reliable.

A hypothesis is a tentative explanation for a phenomenon; testable hypotheses have clearly defined concepts (operational definitions), are not circular, and refer to concepts that can be observed.

Goals of the Scientific Method

The scientific method is intended to meet four goals: description, prediction, explanation, and application.

Description

Psychologists seek to describe events and relationships between variables; most often, researchers use the nomothetic approach and quantitative analysis.

Prediction

Correlational relationships allow psychologists to predict behavior or events but do not allow psychologists to infer what causes these relationships.

Explanation

Psychologists understand the cause of a phenomenon when the three conditions for causal inference are met: covariation, time-order relationship, and elimination of plausible alternative causes.

The experimental method, in which researchers manipulate independent variables to determine their effect on dependent variables, establishes time-order and allows a clearer determination of covariation.

Plausible alternative causes for a relationship are eliminated if there are no confoundings in a study.

Researchers seek to generalize a study's findings to describe different populations, settings, and conditions.

Application

In applied research, psychologists apply their knowledge and research methods to improve people's lives; psychologists conduct basic research to gain knowledge about behavior and mental processes and to test theories.

Scientific Theory Construction and Testing

Theories are proposed explanations for the causes of phenomena and vary in scope and level of explanation.

A scientific theory is a logically organized set of propositions that defines events, describes relationships among events, and explains the occurrence of events.

Successful scientific theories organize empirical knowledge, guide research by offering testable hypotheses, and survive rigorous testing.

Researchers evaluate theories by judging the theory's internal consistency, observing whether hypothesized outcomes occur when the theory is tested, and noting whether the theory makes precise predictions based on parsimonious explanations.