Chapter 1 : Introduction

[NOTE: Numbers in parentheses refer to pages in the fifth edition of Research Methods in Psychology by Shaughnessy, Zechmeister, and Zechmeister (2000), where these concepts and ideas are more fully defined.]

causal inference The identification of the cause or causes of a phenomenon, by establishing covariation of cause and effect, a time-order relationship with the cause preceding the effect, and the elimination of plausible alternative causes. (25)

confounding When the independent variable of interest systematically covaries with a second, unintended independent variable. (27)

control A key component of the scientific method whereby the effect of various factors possibly responsible for a phenomenon are isolated; three basic types of control are manipulation, holding conditions constant, and balancing. (9)

correlation A correlation exists when two different measures of the same people, events, or things vary together; the presence of a correlation makes it possible to predict values on one variable by knowing the values on the second variable. (24)

dependent variable Measure of behavior used by the researcher to assess the effect (if any) of the independent variables. (10)

empirical approach An approach to acquiring knowledge that emphasizes direct observation and experimentation as a way of answering questions. (7)

external validity The extent to which the results of a research study can be generalized to different populations, settings, and conditions. (27)

hypothesis A tentative explanation for a phenomenon. (17)

independent variable A factor for which the researcher either selects or manipulates at least two levels in order to determine its effect on behavior. (9)

individual differences variable A characteristic or trait that varies consistently across individuals (e.g., age, depression, gender, intelligence); individual difference variables (subject variables) are often studied as independent variables in the natural groups design. Thus, these variables are sometimes called natural groups variables. (10)

internal validity The degree to which differences in performance can be attributed unambiguously to an effect of an independent variable, as opposed to an effect of some other (uncontrolled) variable; an internally valid study is free of confounds. (27)

operational definition A procedure whereby a concept is defined solely in terms of the operations used to produce and measure it. (13)

reliability A measure is reliable when it is consistent. (16)

scientific method An approach to knowledge that emphasizes empirical rather than intuitive processes, testable hypotheses, systematic and controlled observation of operationally defined phenomena, data collection using accurate and precise instrumentation, valid and reliable measures, and objective reporting of results; scientists tend to be critical and, most importantly, skeptical. (5)

theory A logically organized set of propositions which serves to define events, describe relationships among events, and explain the occurrence of these events; scientific theories guide research and organize empirical knowledge. (30)

validity The "truthfulness" of a measure; a valid measure is one that measures what it claims to measure. (15)

**********

Psychology as a Science (3)

• The scope of scientific psychology has increased dramatically in the 100-plus years since its inception.
• The American Psychological Association (APA) and the American Psychological Society (APS) promote the science of psychology.

• Psychologists use the scientific method to gain knowledge about human and animal behavior.
• The scientific method differs from nonscientific ("everyday") approaches to gaining knowledge.

• The scientific method is empirical and requires systematic, controlled observation.
• To achieve control in a research situation, researchers manipulate independent variables or select levels of individual differences 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 concepts 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.
• Scientists adopt a skeptical attitude and are cautious about accepting explanations until sufficient empirical evidence is obtained.

• The scientific method is intended to meet three goals: description, prediction, and understanding.
• Psychologists seek to describe events and relationships between variables; most often, researchers use the nomothetic approach and quantitative analysis.
• Correlational relationships allow psychologists to predict behavior or events, but do not allow psychologists to infer what causes these relationships.
• Psychologists understand the cause of a phenomenon when the three conditions for causal inferences 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 for a clearer determination of covariation.
• Plausible alternative causes for a relationship are eliminated if there are no confoundings in a study; a study free of confoundings has internal validity.
• External validity refers to the extent to which a study's findings may be used to describe different populations, settings, and conditions.

• Theories, proposed explanations for the causes of behavior, vary in their scope and their 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.
• Theories frequently posit intervening variables to explain observed behavior.
• 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.

• Psychologists are obligated to conduct research of the highest integrity.
• The American Psychological Association (APA) has adopted a code of ethics to guide the professional behavior of psychologists.