Experimental Research
Download
Report
Transcript Experimental Research
Chapter 2: The Research
Enterprise in Psychology
The Scientific Approach:
A Search for Laws
Basic assumption: events are governed by
some lawful order
Goals:
1. Measurement and description
2. Understanding and prediction
3. Application and control
Figure 2.2 Flowchart of
steps in a scientific
investigation
The Scientific Method: Terminology
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
Table 2.1 Key Data Collection Techniques in Psychology
The Scientific Method: Terminology
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
Research methods: General strategies for
conducting scientific studies
Peer Review of Scientific Articles
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.
Experimental Research: Looking for Causes
Experiment = manipulation of one variable
under controlled conditions so that resulting
changes in another variable can be observed
Detection of cause-and-effect relationships
Independent variable (IV) = variable
manipulated
Dependent variable (DV) = variable affected
by manipulation
How does X affect Y?
X = Independent Variable, and Y =
Dependent Variable
Experimental and Control Groups:
The Logic of the Scientific Method
Experimental group
Control group
Random assignment
Manipulate independent variable for one
group only
Resulting differences in the two groups
must be due to the independent variable
Extraneous and confounding variables
Figure 2.6 The basic elements of an experiment
Advantages and Disadvantages
of Experimental Research
Strengths:
conclusions about cause-and-effect can be
drawn
Weaknesses:
artificial nature of experiments
ethical and practical issues
Descriptive/Correlational Methods:
Looking for Relationships
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
Statistics and Research:
Drawing Conclusions
Statistics – using mathematics to organize,
summarize, and interpret numerical data
Descriptive statistics: organizing and
summarizing data
Inferential statistics: interpreting data and
drawing conclusions
Descriptive Statistics:
Measures of Central Tendency
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?
Figure 2.11 Measures of central tendency
Descriptive Statistics: Correlation
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
Figure 2.13 Positive and negative correlation
Figure 2.14 Interpreting correlation coefficients
Correlation:
Prediction, Not Causation
Higher correlation coefficients = increased ability
to predict one variable based on the other
SAT/ACT scores moderately correlated with
first year college GPA
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
Inferential Statistics:
Interpreting Data/Drawing Conclusions
Hypothesis testing: do observed findings
support the hypotheses?
Are findings real or due to chance?
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
Evaluating Research:
Methodological Pitfalls
Sampling bias
Placebo effects
Distortions in self-report data:
Social desirability bias
Response set
Experimenter bias
the double-blind solution
Ethics in Psychological Research:
Do the Ends Justify the Means?
The question of deception
The question of animal research
Controversy among psychologists and the
public
Ethical standards for research: the American
Psychological Association
Ensures both human and animal subjects
are treated with dignity
Figure 2.17 Ethics in research
The Internet and Psychological Research
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
The Internet and Psychological Research
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