Transcript Table of Contents Table of Contents

Chapter 2
The Research Enterprise in
Psychology
The Scientific Approach: A Search for
Laws
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Empiricism
Basic assumption: events are governed by some
lawful order
Goals:
– Measurement and description
– Understanding and prediction
– Application and control
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Goal of theory testing in science: refutation not
proving – Karl Popper
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Five steps of
the Scientific
Method
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The Scientific Method: Terminology
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Operational definitions are used to clarify precisely
what is meant by each variable
 Participants or subjects are the organisms whose
behavior is systematically observed in a study
 Data collection techniques allow for empirical
observation and measurement
 Statistics are used to analyze data and decide
whether hypotheses were supported
 Findings are shared through reports at scientific
meetings and in scientific journals – periodicals
that publish technical and scholarly material
– Advantages of the scientific method: clarity of communication and relative
intolerance of error
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Research methods: general strategies for
conducting scientific studies
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Peer Review of Scientific Articles
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The process of publishing scientific studies
allows other experts to evaluate and critique
new research findings.
 They carefully evaluate each study’s
methods, statistical analyses, and
conclusions, as well as its contribution to
knowledge and theory.
 The purpose of the peer review process is to
ensure that journals publish reliable findings
based on high-quality research.
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Figure 2.4 The peer
review process for
journal submissions.
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Experimental Research: Looking for
Causes
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Experiment = manipulation of one variable under
controlled conditions so that resulting changes in
another variable can be observed
– Detection of cause-and-effect relationships
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Independent variable (IV) = variable manipulated
Dependent variable (DV) = variable affected by
manipulation
– How does X affect Y?
– X= Independent Variable, and Y= Dependent Variable
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Experimental and Control Groups:
The Logic of the Scientific Method
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Experimental group – subjects who receive some
special treatment in regard to the independent
variable
Control group – similar subjects who do not receive
the special treatment
– Logic:
• Two groups alike in all respects (random assignment)
• Manipulate independent variable for one group only
• Resulting differences in the two groups must be due to the
independent variable
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ExtraneousVariable: variable, other than the independent
variable, that may influence the dependent variable.
 Confounding variables: occurs when participants in one
group of subjects are inadvertently different in some way from
participants in the other group, influencing outcome.
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The basic elements of an experiment
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Experimental Designs: Variations
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Expose a single group to two different conditions
– Reduces extraneous variables
Manipulate more than one independent variable
– Allows for study of interactions between variables
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Use more than one dependent variable
– Obtains a more complete picture of effect of the independent
variable
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Manipulation of two independent variables in an experiment
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Strengths and Weaknesses of
Experimental Research
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Strengths:
– conclusions about cause-and-effect can be drawn
– Probabilistic causality
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Weaknesses:
– artificial nature of experiments
– ethical and practical issues
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Descriptive/Correlational Methods:
Looking for Relationships
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Methods used when a researcher cannot manipulate
the variables under study
• Naturalistic observation
• Case studies
• Surveys
– Allow researchers to describe patterns of behavior and
discover links or associations between variables but cannot
imply causation
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Statistics and Research: Drawing
Conclusions
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Statistics – using mathematics to organize,
summarize, and interpret numerical data
• Descriptive statistics: organizing and summarizing
data
• Inferential statistics: interpreting data and drawing
conclusions – use of probability
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Descriptive Statistics: Measures of
Central Tendency
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Measures of central tendency = typical or average
score in a distribution
Mean: arithmetic average of scores
Median: score falling in the exact center
Mode: most frequently occurring score
– Which most accurately depicts the typical?
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Descriptive Statistics: Variability
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Variability = how much scores vary from each other
and from the mean
– Standard deviation = numerical depiction of variability
• High variability in data set = high standard deviation
• Low variability in data set = low standard deviation
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Descriptive Statistics: Correlation
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When two variables are related to each other, they
are correlated.
Correlation = numerical index of degree of
relationship
– Correlation expressed as a number between 0 and 1
– Can be positive or negative
– Numbers closer to 1 (+ or -) indicate stronger relationship
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Figure 2.13 Positive and negative correlation
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Correlation: Prediction, Not
Causation
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Higher correlation coefficients = increased ability to
predict one variable based on the other
– SAT/ACT scores moderately correlated with first year
college GPA
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2 variables may be highly correlated, but not causally
related
– Foot size and vocabulary positively correlated
– Do larger feet cause larger vocabularies?
– The third variable problem
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Inferential Statistics: Interpreting
Data and Drawing Conclusions
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Hypothesis testing: do observed findings support the
hypotheses?
– Are findings real or due to chance?
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Statistical significance = when the probability that the
observed findings are due to chance is very low
– Very low = less than 5 chances in 100/ .05 level
– Other factors might account for the results
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Evaluating Research: Methodological
Pitfalls
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Sampling bias a sample is not representative of the population
Placebo effect when a participant’s expectations lead them to
experience some change even though they receive empty, fake, or
ineffectual treatment
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Distortions in self-report data:
– Social desirability bias socially approved answers to questions
about oneself
– Response set tendency to respond to questions in a particular way
(agree with everything, etc.).
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Experimenter bias
– the double-blind solution
– Research protocol of clinical trial for drugs – FDA in U.S.
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The Internet and Psychological Research
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Internet-mediated research refers to studies in which
data collection occurs over the web.
Possible Advantages
– Samples that are much larger and much more diverse than
the samples typically used in laboratory research
– Have the potential to yield more diverse and representative
samples
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Potential Disadvantages
– Sampling bias resulting from self-selection may be a more
troublesome issue in Internet-mediated research
• Web users tend to be younger, brighter, and more affluent than
nonusers
– Data are collected under far less controlled conditions than
in traditional studies
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Ethics in Psychological Research: Do
the Ends Justify the Means?
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The question of deception
 The question of animal research
– Controversy among psychologists and the public
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Ethical standards for research: the American
Psychological Association
– Ensures both human and animal subjects are
treated with dignity
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