Basic Concepts of Research Basis of scientific method Making observations in systematic way Follow strict rules of evidence Critical thinking about evidence Research Methods In Psychology

Empirical Evidence and Operational Definitions Empirical evidence – observations of publicly (confirmable) observable behavior Operational definitions – use operations of measurement to describe observations Evaluates quality of evidence and allows alternative interpretations Research Methods In Psychology

Theories and Hypotheses Theories – tentative explanations of facts and relationships in science Hypothesis – a prediction based on a theory Tested to confirm or refute Can be revised or abandoned Research Methods In Psychology

Representativeness of Samples Sample Representative of larger group or population of interest Small group of humans or animals Unrepresentative sample – misleading or biased test of hypothesis Replication of research removes most doubt Research Methods In Psychology

Research Methods Descriptive studies Simplest method of scientific inquiry Describe behavior and mental processes Most widely used Survey method – ask people’s opinions Naturalistic observation – watch, describe Clinical method – observe in clinic setting All have advantages and disadvantages Research Methods In Psychology

Research Methods Correlational Studies Correlational method: measure two variables for statistical relationship Variable: anything that can be assigned a numerical value Uses quantitative measures Research Methods In Psychology

Research Methods Correlational Studies Correlation coefficient Measures each variable Indicates strength ( 0 to  1) and direction (negative or positive) of relationship Correlation does not mean causation Research Methods In Psychology

Fig. 2.2 Variable 2 21 Variable Hypothetical data illustrating a correlation coefficient of +1.00

Fig. 2.3 Hypothetical data illustrating a correlation coefficient of Variable 2 21 Variable

Fig. 2.4 Hypothetical data illustrating a correlation coefficient of zero Variable 2 21 Variable

Formal Experiments Tests relationship of two or more variables Allows conclusions about cause-and-effect Quantitative measures of behavior compared in different conditions created by researchers Evidence supports or rejects hypothesis Research Methods In Psychology

Formal Experiments Elements Independent variable – gets manipulated Dependent variable – amount of change Experimental group – exposed to independent variable or conditions expected to create change Control group – presents normal behavior used for comparison Random assignment Experimental control Research Methods In Psychology

0.02 Nonviolent film Violent film Fig. 2.6

Fig. 2.7 Control group: View nonviolent film Randomly assign into control and experimental groups Full population of interest Experimental group: exposed to independent variable: view violent film

Formal Experiments Placebo control Placebo effect: provides no active effect Use in identical conditions for control and experimental groups Blind experiment Researchers blind to group membership of participants to rule out experimenter bias Strongest experiments – double blind Researchers and participants kept blind Research Methods In Psychology

Describing and Interpreting Data Descriptive statistics – summarized data for large groups of participants Mean: average Median: midpoint in rank-ordered data Mode: score appearing most often Normal distribution: bell-shaped curve Standard deviation: degree to which scores in ordered distribution are spread out Research Methods In Psychology

% Giving birth for 1st time Mother’s Age Mode Mean & Median

Describing and Interpreting Data Reaching conclusions from data Statistical significance Size of correlation Difference of means are greater than chance Two issues for significance Larger sample size is better Statistical difference does not equal practical significance Research Methods In Psychology

Ethical Principles of Research Ethics in research with human participants Freedom from coercion Informed consent Limited deception Adequate debriefing Confidentiality Research Methods In Psychology

Ethical Principles of Research Ethics of research with nonhuman animals Necessity Health Humane treatment Research Methods In Psychology

Human Diversity: Equal Representation in Research U.S. National Institutes of Health New applications for research grants involving human subjects must include diverse samples of Both sexes Major racial and cultural groups Differences may be real and important Research Methods In Psychology