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Copyright © Allyn & Bacon 2007
Chapter 2Chapter 2
Research Methods
This multimedia product and its contents are protected under copyright law. The following are prohibited by law:
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• ISBN: 0-131-73180-7
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Why the Scientific Approach?Why the Scientific Approach?
Psychology is different from pseudosciences because it takes the scientific approach to its research. None of the pseudosciences have survived by the scientific method.
Psychologists reject approaches that claim to have “evidence” but offer only anecdotes and testimonials.
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How Do Psychologists How Do Psychologists Develop New Knowledge?Develop New Knowledge?
Psychologists, like researchers in all other
sciences, use the scientific method to test their ideas
empirically
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Empirical investigation – An approach to research that relies on sensory experience and observation as research data
How Do Psychologists How Do Psychologists Develop New Knowledge?Develop New Knowledge?
Scientific method –A five-step process for empirical investigation of a hypothesis under conditions designed to control biases and subjective judgments
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TheoryTheory
A theory is a testable explanation for a set of facts or observations.
Examples are: Einstein’s theory of relativity, germ theory of disease, Darwin’s theory of natural selection, social learning theory
Theory doesn’t just simply mean a “hunch” like in everyday language.
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Emily Rosa and Therapeutic TouchEmily Rosa and Therapeutic Touch
Emily Rosa, a fourth grader, became the youngest published researcher.
Her science project challenged TT, a treatment that her mother (a nurse) had explained to her.
Emily used the scientific method to examine claims that TT could heal individuals.
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The Five Steps of the Scientific MethodThe Five Steps of the Scientific Method
Developing a hypothesisDeveloping a hypothesis
Performing a controlled testPerforming a controlled test
Gathering objective dataGathering objective data
Analyzing the resultsAnalyzing the results
Publishing, criticizing, and Publishing, criticizing, and replicating the resultsreplicating the results
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Developing a Developing a hypothesishypothesis
Performing a controlled test
Gathering objective data
Analyzing the results
Publishing, criticizing, and replicating the
results
Hypothesis –A statement predicting the outcome of a scientific study
Operational definitions –Exact procedures used in establishing experimental conditions and measurement of results
The Five Steps of the Scientific MethodThe Five Steps of the Scientific Method
Copyright © Allyn & Bacon 2007
Developing a hypothesis
Performing a Performing a controlled testcontrolled test
Gathering objective data
Analyzing the results
Publishing, criticizing, and replicating the
results
Independent variable –The variable manipulated by the experimenter
Random presentation –Using chance alone to determine the order in which the stimulus is presented
The Five Steps of the Scientific MethodThe Five Steps of the Scientific Method
Copyright © Allyn & Bacon 2007
Developing a hypothesis
Performing a controlled test
Gathering Gathering objective dataobjective data
Analyzing the results
Publishing, criticizing, and replicating the
results
Data –Information gathered by researcher and used to test a hypothesis
Dependent variable –The measured outcome of a study; the responses of participants in a study
The Five Steps of the Scientific MethodThe Five Steps of the Scientific Method
Copyright © Allyn & Bacon 2007
Developing a hypothesis
Performing a controlled test
Gathering objective data
Analyzing the Analyzing the resultsresults
Publishing, criticizing, and replicating the
results
Based on statistical analyses of results, the hypothesis is accepted or rejected
The Five Steps of the Scientific MethodThe Five Steps of the Scientific Method
Copyright © Allyn & Bacon 2007
Developing a hypothesis
Performing a controlled test
Gathering objective data
Analyzing the results
Publishing, Publishing, criticizing, and criticizing, and replicating the replicating the
resultsresults
The Five Steps of the Scientific MethodThe Five Steps of the Scientific Method
Researchers must find out whether their work can withstand the scrutiny of the scientific community
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Types of Psychological ResearchTypes of Psychological Research
In experiments, the researcher controls all the conditions and directly manipulates the conditions
Non-experimental methods include:• Correlational studies…relationship between variables• Surveys…asking individuals to respond about self• Naturalistic observation…collect data unseen• Longitudinal studies…group is followed over time• Cross-sectional studies…one given time, different ages• Cohort-sequential studies…different ages followed brief time• Ex-post facto design…there is a condition due to ethics
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Some terms involved in the experimental Some terms involved in the experimental method…method…
Basic inquiry
Hypothesis
Literature
Confounding or extraneous variables
Controls
Subject selection
Representative sample
Random assignment
Double-blind
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Sources of BiasSources of Bias
Sources of bias include:Personal bias…beliefs, preferences, prejudices
Expectancy bias…looking for certain outcomes
Bias could affect the way an experimenter designs a study, collects data, or interprets results
Double blind studies attempt to control bias
Researchers must also attempt to control confounding variables
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Ethics in ResearchEthics in Research
APA: “Ethical Principles of Psychologists and Code of Conduct”
Each institution must have IRB
Animal research must be approved by IACUC
Deception…some is fine but needs debriefing
Debriefing…study is explained and it should be made sure that individuals suffer no ill effects
Animal research…debate continues
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Questions Science Cannot AnswerQuestions Science Cannot Answer
The scientific method is not appropriate for answering questions that cannot be put to an objective, empirical test• Ethics• Morality• Religious beliefs• Preferences
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How Do We Make Sense of How Do We Make Sense of the Data?the Data?
Researchers use statistics for two major purposes:
(1) descriptively to characterize measurements made on groups
or individuals and(2) inferentially to judge whether
these measurements are the result of chance
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Organizing the DataOrganizing the Data
First results must be arranged in a summary chart known as a frequency distribution
We can convert the data into a bar graph called a histogram
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Describing the Data With Descriptive Describing the Data With Descriptive StatisticsStatistics
Descriptive statistics include:• The mean (measure of central tendency)—adding all scores
and dividing by the number of scores• The median (measure of central tendency)—the score that
separates the upper half of the scores from the lower half• The mode (measure of central tendency)—score that occurs
more often than all• The range (measure of variability)—difference between
highest and lowest values• The standard deviation (measure of variability)—average
difference between scores and the mean• The normal distribution—bell-shaped curve describing the
spread of scores…approximately 34% 34% 13% 13% 2% 2%
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Correlations: A relationship between Correlations: A relationship between Two VariablesTwo Variables
Correlation–A relationship between two variables, in which changes in one variable are reflected in changes in the other variable
Correlation coefficient–A number between -1 and +1 expressing the degree of relationship between two variables
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Making Inferences with inferential Making Inferences with inferential statisticsstatistics
Inferential statistics are used to assess whether the results of a study are significant or whether they might be simply the result of chance…this is usually the deciding factor whether or not to reject or accept a hypothesis
Statistical significance or difference—the probability that it might be due to chance is less than 5 in a 100…p<.05