introductory psychology: research design

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lecture 3 from a college level introduction to psychology course taught Fall 2011 by Brian J. Piper, Ph.D. ( at Willamette University, includes correlation and experiments


  • 1. Thinking Critically Brian J. Piper, Ph.D.

2. Theory A theory is an explanation that integratesprinciples and organizes and predictsbehavior or events.For example, low self-esteem contributes to depression. 3. HypothesisA hypothesis is a testable prediction, oftenprompted by a theory, to enable us toaccept, reject or revise the theory.People with low self-esteem are apt to feelmore depressed. 4. Research Observations Research would require us to administertests of self-esteem and depression.Individuals who score low on a self-esteem test and high on a depression test wouldconfirm our hypothesis. 5. Research Process 6. Description Case StudyA technique in which one person is studied in depth to reveal underlying behavioral principles. Susan Kuklin/ Photo ResearchersIs language uniquely human? 7. Case Study A case study canprovide a uniqueopportunity toanswer questionsthat might bedifficult with othermethods. Henry Gustav Molaison (1926-2008) 8. SurveyA technique for ascertaining the self-reportedattitudes, opinions or behaviors of peopleusually done by questioning a representative,random sample of people. 9. Survey Wording Effects Wording can change the results of a survey. Q: Should cigarette ads and pornography beallowed on television? (not allowed vs. forbid) 10. Survey Random Sampling If each member of a population has an equalchance of inclusion into a sample, it is called arandom sample(unbiased). If the survey sample is biased, itsresults are not valid.The fastest way to know about themarble color ratio is to blindly transfer a few into a smaller jar andcount them. 11. Polls Can be extremelyaccurate whencarefully conducted. 12. Naturalistic ObservationObserving and recording the behavior of animals in thewild and recording self-seating patterns in a multiracial school lunch room constitute naturalistic observation.Courtesy of Gilda Morelli 13. Descriptive MethodsSummaryCase studies, surveys, and naturalistic observation describe behaviors. 14. CorrelationWhen one trait or behavior accompaniesanother, we say the two correlate.Indicates strengthof relationship (0.00 to 1.00) Correlation coefficientr = + 0.37Correlation Coefficient is a statistical measure of the Indicates directionrelationship between twoof relationshipvariables. (positive or negative) 15. Scatterplots Perfect positivecorrelation (?_.__)Scatterplot is a graph comprised of points that aregenerated by values of two variables. The slope ofthe points depicts the direction, while the amountof scatter depicts the strength of the relationship. 16. Scatterplots Perfect negativeNo relationship (_.__)correlation (?_.__) The Scatterplot on the left shows a ______ correlation,while the one on the right shows _____ _______ betweenthe two variables. 17. DataData showing height and temperament in people. 18. Scatterplot The Scatterplot below shows the relationshipbetween height and temperament in people. Thereis a moderate positive correlation of _.__. 19. Scatterplot The Scatterplot below shows the relationshipbetween height and temperament in people. Thereis a moderate positive correlation of +0.63. 20. Correlation and Causation Correlation does not mean causation! or 21. Order in Random Events Given random data, we look for order and meaningful patterns.Your chances of being dealt either of these hands isprecisely the same: 1 in 2,598,960. 22. Order in Random Events Given large numbers of random outcomes, a feware likely to express order. Jerry Telfer/ San Francisco Chronicle Angelo and Maria Gallina won twoMany people have been struck byCalifornia lottery games on the same day.lightening 2+ times. 23. ExperimentationExploring Cause and Effect Like other sciences, experimentation is thebackbone of psychological research. Experiments isolate causes and their effects. 24. Exploring Cause & EffectMany factors influence our behavior. Experiments(1) manipulate factors that interest us, while otherfactors are kept under (2) control. Effects generated by manipulated factors isolatecause and effect relationships. 25. Evaluating TherapiesDouble-blind ProcedureIn evaluating drug therapies, patients and experimenters assistants should remainunaware of which patients had the realtreatment and which patients had the placebo treatment.Examples: surgery & accupuncture 26. Evaluating Therapies Random AssignmentAssigning participants to experimental (breast- fed) and control (formula-fed) conditions by random assignment minimizes pre-existing differences between the two groups. 27. Independent Variable An independent variable is a factor manipulatedby the experimenter. The effect of the independent variable is the focus of the study.For example, when examining the effects of breastfeeding upon intelligence, breast feeding is the independent variable. 28. Dependent VariableA dependent variable is a factor that may change in response to an independent variable. In psychology, it is usually a behavior or a mental process.For example, in our study on the effect of breastfeeding upon intelligence, intelligence is thedependent variable. 29. ExperimentationA summary of steps during experimentation. 30. Characteristics of Good Experiments Experimental & Control Group Randomization Double-blind 31. ComparisonBelow is a comparison of different researchmethods. 32. Correlation: Designversus statistic (r) Marmosets arerandomly assigned togroups to receivedifferent doses ofmethamphetamineand their motoractivity is recorded. 33. Example A research study examines whethersmoking during pregnancyinfluences child behavior. Thesample consists of moms thatrespond to a Craigslist posting. What is the independentvariable? What is the dependent variable? Is the research designcorrelational or experimental?Piper et al. (2011) Drug & Alcohol Dependence. 34. Describing DataA meaningful description of data is important in research. Misrepresentation may lead toincorrect conclusions. 35. Measures of Central TendencyMode: The most frequently occurring scorein a distribution.Mean: The arithmetic average of scores in adistribution obtained by adding thescores and then dividing by the numberof scores that were added together.Median: The middle score in a rank-ordereddistribution. 36. Normal CurveA symmetrical, bell-shaped curve thatdescribes the distribution of many types ofdata (normal distribution). Most scores fallnear the mean. 37. Measures of Central TendencyA Skewed Distribution 38. Measures of VariationRange: The difference between the highest andlowest scores in a distribution.Standard Deviation: A computed measure ofhow much scores vary around the mean. 39. Standard Deviation 40. Illusion of ControlThat chance events are subject to personal control is anillusion of control fed by: Illusory Correlation: the perception of a relationshipwhere no relationship actually exists (e.g. vaccines& autism). Regression Toward the Mean: the tendency forextremes of unusual scores or events to regresstoward the average. 41. Making InferencesA statistical statement of how frequently an obtained result occurred by experimental manipulation or by chance.P valueDecision.80Not significant.20Not significant.060 Not significant.049 Significant!.001 Significant!.000000000005Significant! 42. Making InferencesWhen is an Observed Difference Reliable?1. Representative samples are better than biased samples.2. Less-variable observations are more reliable than more variable ones.3. More cases are better than fewer cases. 43. Making Inferences When is a Difference Significant?When sample averages are reliable and thedifference between them is relatively large, we say the difference has statistical significance. It is probably not due to chance variation.For psychologists this difference is measured through alpha level set at 5 percent. 44. Example A research study examines whethersmoking during pregnancy influenceschild behavior. The sample consistsof moms that respond to a Craigslistposting. What is the independent variable? Maternal smoking (+/-) What is the dependent variable? child behavior/academics Is the research design correlational or experimental? correlational Piper et al. (2011) Drug & Alcohol Dependence. 45. Clever Hans The German horse owner Wilhelm vonOsten was believed to have taught Hansto do simple mathematics. The psychologist Oskar Pfungstinvestigated in 1907. Osten never believed Pfungsts findings.Pfungst, O. (1911). Clever Hans (The horse of Mr. von Osten): A contribution to experimental animal and humanpsychology (Trans. C. L. Rahn). New York: Henry Holt. (Originally published in German, 1907). 46. Frequently Asked Questions About Psychology Q1. Can laboratory experiments illuminateeveryday life?Ans: Artificial laboratory conditions are created tostudy behavior in simplistic terms. The goal is tofind underlying principles that govern behavior. 47. FAQQ2. Does behavior depend on ones culture and gender?Ans: Even when specific attitudes and behaviors vary acrosscultures, as they often do, the underlying processes are muchthe same. Biology determines our sex, and culture furtherbends the genders. However, in many ways woman and man are similarly human. Ami Vitale/ Getty Images 48. FAQQ3. Why do psychologists study animals, and is it ethical toexperiment on animals?Ans: Studying animals gives us the understanding of manybehaviors that may have common biology across animalsand humans. From animal studies, we have gained insights to devastating and fatal diseases. All researchers who deal with animal research are required to follow ethicalguidelines in caring for these animals. RRR D. Shapiro, Wildlife Conservation Society 49. FAQ Q4. Is it ethical to experiment on people?Ans: Yes. Experiments that do not involve anykind of physical or psychological harm beyondno