The Purpose of Psychological Research
Theory- Ascientific theory is a logical explanation for all the relevant data or facts scientists have
observed regarding certain natural phenomena.
• Must be testable and refutable
Hypothesis- Astatement that proposes the existence of a relationship between variables, typically as a
tentative explanation for cause and effect, hypotheses are often designed to be tested by research.
Basic Research- Research that tests theories or hypotheses
• Research done for the love of science
Applied Research- Research to solve a problem
• Research performed is applied to everyday problems
◦ Clinical and counseling psychology
◦ Business, workplace applications
Replication Studies- Research conducted for the purpose of verifying previous findings
• Backbone of good science
• Important because the results of a study can vary considerably depending on
experimental conditions and the research method used.
Case Study- Method of research that involves in-depth study of one or more subjects who are
examined individually using direct observation, testing, experimentation, and other methods.
Limitations of the Case Study
• Lack of investigative control
• Potential for subjective bias by researcher
• Focus is on small samples or one individual case
◦ Difficult to generalize to other people
Surveys and Questionaires
Survey- Research method that provides descriptive information in which a representative sample of
people is questioned about their behaviors or attitudes.
How SamplesAre Selected for Surveys
Sample- Selected segment of a larger population that is being studied in psychological research • Two kinds of samples are the representative and random sample
Representative Sample- Asample in which critical subgroups are represented according to their
incidence in the larger population that researcher is studying.
Random Sample- Sample group of a larger population that is selected by randomization procedures
• Arandom sample differs fro a representative sample.
Limits of the Survey Method
• Demographic bias
• Sex bias
• Question design
◦ Double-barreled questions
▪ Are you voting this year, and do you smoke?
• Surveys cannot look closely at specific individuals.
The Observational Method
Observational Method- Method of psychological research, providing descriptive information, in
which subjects are observed as they go about their usual activities.
Naturalistic Observation- Psychological research using the observational method that takes place in a
natural setting such as the subject's home or school environment.
Limitations of the Observational Method
Observer Bias- Tendency of an observer to read more into a situation than is actually there or to see
what he or she expects to see.
• Halo effect
Observer Effect- The tendency of subjects to modify behavior because they are aware they are being
Correlational Method- Research method that uses statistical techniques to determine the degree of
relationship between variables.
Variable- Anything that changes or varies.
Coefficient of Correlation- Statistic used to describe the degree of relationship between two or more variables in which positive correlations indicate that variables vary together in the same direction and
negative correlations indicate the opposite.
Interpreting a Negative Correlation Between Variables
The correlation coefficient ranges from +1.00 to -1.00 Zero and absolute values near zero indicate no
◦ As the absolute value increases toward +1.00 or -1.00, the strength of the relationship
◦ +1.0 is a perfect positive correlation.
◦ -1.0 is a perfect negative correlation
• Anegative correlation indicates that increases in one measure are associated with decreases in
Limitations of Correlational Studies
• Correlation does not mean causation.
• Athird factor may be involved.
• It does not allow for precise control over the various factors that may influence the behavior
Experimental Research Methods
Experimental Research- Research is conducted in precisely controlled laboratory conditions in which
subjects are confronted with specific stimuli, and their reactions are carefully measured to discover
relationships among variables.
Independent and Dependent Variables
Independent Variables (cause)- Condition or factor that the experimenter manipulates in order to
determine whether changes in behavior (the dependent variable) result.
Dependent Variable (effect)- In experimental research, the behavior that results from manipulation of
an independent variable.
Experimental and Control Groups
Experimental Group- In experimental research, a group of subjects are exposed to different varieties
of independent variables, so that resulting behaviors can be compared.
Control Group- In experimental psychology, a group of subjects experience all the same conditions as
subjects experience all the same conditions as subjects in the experimental group except for the key
factor (independent variable) the researcher is evaluating. Example of the Experimental and Control Groups
• Astudy on depression has 200 volunteers
◦ Hypothesis is that 75 mg of Grug X will result in a 50% decrease i