Basic Concepts of Research

Basis of scientific method

Making observations in systematic way

Follow strict rules of evidence

Critical thinking about evidence

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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

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Theories and HypothesesTheories – tentative explanations of facts

and relationships in science

Hypothesis – a prediction based on a theoryTested to confirm or refuteCan be revised or abandoned

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Representativeness of SamplesSample

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

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Research MethodsDescriptive 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

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Research MethodsCorrelational Studies

Correlational method: measure two variables for statistical relationship

Variable: anything that can be assigned a numerical value

Uses quantitative measures

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Research MethodsCorrelational 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. 2.2V

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Hypothetical data illustrating

a correlation coefficient of

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Fig. 2.3

Hypothetical data illustrating

a correlation coefficient of

-1.00

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Fig. 2.4

Hypothetical data illustrating

a correlation coefficient of

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Formal ExperimentsTests 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

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Formal ExperimentsElements

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

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0.02

Nonviolent film

Violent film

0.04

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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 ExperimentsPlacebo control

Placebo effect: provides no active effectUse in identical conditions for control and

experimental groups

Blind experimentResearchers blind to group membership of

participants to rule out experimenter bias

Strongest experiments – double blindResearchers and participants kept blind

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Describing and Interpreting DataDescriptive 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

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1

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13 16 19 22 25 28 31 34 37

% G

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Mother’s Age

ModeMean & Median

Describing and Interpreting DataReaching 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

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Ethical Principles of ResearchEthics in research with human participants

Freedom from coercion

Informed consent

Limited deception

Adequate debriefing

Confidentiality

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Ethical Principles of Research

Ethics of research with nonhuman

animals

Necessity

Health

Humane treatment

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Human Diversity: Equal Representation in ResearchU.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

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Research Methods In Psychology