PSY Chapter two 01/13/2013
• The scientific method: reflects a cyclical relationship among a theory, a testable hypothesis
derived from the theory, research conducted to test the hypothesis, and adjustments to the theory as
findings prompt reevolution. A good theory evolves over time, and the result is an increasingly accurate
model of some phenomenon.
What is scientific Inquiry?
• Is a way of finding answers to empirical questionsquestions that can be answered by observing the
world and measuring aspects of it.
• Have 4 basic goals: what happens, when it happens, what causes it to happen, and why it happens.
• *Scientific method: a systematic procedure of observing a measuring phenomena to answer
questions about what happens, when it happens, what causes it, and why.
1) The scientific method depends on theories, hypotheses, and research
*Theory: a model of interconnected ideas and concepts that explains what is observed and
makes predictions about future events.
• *Hypothesis: a specific prediction of what should be observed in the world if a theory is correct.
• *Research: scientific process that involves the systematic and careful collection of data.
• *Data: objective observations or measurements
• In general we can have more confidence in scientific findings when research outcomes are
• *Replication: repetition of an experiment to confirm the results.
Theories should generate hypotheses:
• A good theory produces a wide variety of testable hypotheses.
• Jean Piaget: theory that infant and child development suggested that cognitive development occurs
in a fixed series of “stages”, from birth to adolescents.
• Sigmund Freud: theory that all dreams represent the fulfillment of an unconscious wish. 2) Unexpected Findings can be Vulnerable
• Serendipity: when researches unexpectedly discover something important. Only researchers
who are prepared to recognize their importance will benefit from them.
What Are the Types of Studies in Psychological Research?
• There are 3 main types of designs: descriptive, correlational, and experimental.
• *Variable: something in the world that can be measured and that can vary. Ie) the study of
whether women want to have fun after work include number of hours worked, how much fun the
women have at work, and what they want to do after work, what they actually do after work,
whether they rate what they do as having fun, etc.
• Operational definitions: identify and quantify variables so they can be measured.
1) Descriptive Studies Involve Observing and Classifying Behavior
• *Descriptive studies: sometimes called observational studies because of the manner in
which the data typically are collected, involve observing and noting behavior to analyze it’s
• There are 2 basic types of descriptive studies:
• *Naturalistic observation: A passive descriptive study in which observers do not change or
alter ongoing behavior.
• *Participant observation: A type of descriptive study in which the researcher is actively
involved in the situation.
• Descriptive techniques are especially valuable in the early stages of research, when researchers
simply are trying to see whether a phenomenon exists.
• *Longitudinal studies: involve observing and classifying developmental changes that occur
in the same people over time, either with no intervention by the observer or with intervention by the
observer. Ie) assess the abilities of a group of young adults every 5 years. Advantages: provide
information about the effects of age on the same people, allowing researchers to see
developmental change. Disadvantage: expensive, take a long time, and may lose participants over
• *Crosssectional studies: involve observing and classifying developmental changes that
occur in different groups of people at the same time. Advantages: Faster and less expensive than
longitudinal studies. Disadvantages: unidentified variables may be involved (third variable problem,
discussed below). • *Observer bias: systematic errors in observation that occur because of an observer’s
• *Experimenter expectancy effect: actual change in the behavior of the people or animals
being observed that is due to observer bias.
• Researchers observe and describe naturally occurring behaviors to provide a systematic and
2) Correlational Designs Examine How Variables are Related
• *Correlational study: a research method that examines how variables are naturally related in
the real world, without any attempt by the researcher to alter them. Advantages: rely on naturally
occurring relationships. May take place in a realworld setting. Disadvantages: Can’t be used to
support casual relationships (that one thing happened because of the other). Can’t show the
direction of the cause/effect relationship between variables (directionality problem). An unidentified
variable may be involved (third variable problem).
• *Directionality problem: when researchers find a relationship between two variables in a
correlational study, they cannot determine which variable may have caused changed in the other
• Example: sleep (a) and stress (b) are correlated.
Does less sleep cause more stress? (a > b)
Does high stress cause less sleep? (b > a)
• *Third variable problem: when the experimenter cannot directly manipulate the
independent variable and therefore cannot be confident that another, unmeasured variable is not
the actual cause of differences in the dependent variable.
• Example: working long hours (A) is correlated with wanting to have fun after work (B).
Having high energy (C) causes working long hours. (C > A)
Having high energy (C) causes wanting to have fun after work.
(C > B)
• Correlational studies are used to examine how variables are naturally related in the real world, but
cannot be used to establish causality or direction of a relationship (which variable caused changed
in another variable). Correlational reasoning occurs in many contexts, so readers need to be able to
recognize correlational designs in everyday contexts, not just when reading research reports.
3) An Experiment Involves Manipulating Conditions
• *Experiment: a study that tests casual hypotheses by measuring and manipulating variables. • *Control (or comparison) group: the participants in a study that receive no intervention or
an intervention different from the one being studied.
• *Experimental (or treatment) group: the participants in a study that receive the
• *Independent variable: in an experiment, the condition that is manipulated by the
experimenter to examine its impact on the dependent variable.
• *Dependent variable: in an experiment, the measure that is affected by manipulation of the
• *Confound: anything that affects a dependent variable and may unintentionally vary between
the experimental conditions of a study.
1 2 3 4 5
Researcher Researcher Researcher Researcher Conclusion
manipulates… randomly assigns measures… assesses result.
Independent Are the results in The explanation
variable Control Group the control group either supports or
Dependent different from the does not support
Or Variable results in the the hypothesis. Are
experimental there confounds,
Experimental group? which would lead
Group to alternative
explanations? • In an experiment, researchers control the variations in the conditions that the participant
experiences (independent variables) and, measures the outcomes (dependent variables) to gain an
understanding of causality. Researchers need a control group to know if the experiment had an
4) Random Assignment is used to Establish Equivalent Groups
• *Population: everyone in the group the experimenter is interested in.
• *Sample: a subset of a population
• Most of the time a researcher will use convenience sample, which, as the term implies, is a sample
of people who are conveniently available for the study.
• *Selection bias: when participants in differ