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Download 2008 Unit 2 Methods
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II. Research Methods College Board - “Acorn Book” Course Description 6-8% Scientific Bases of Psychology 3 Unit II. Methods Summary Outline A. Experimental, Correlational, and Clinical Research 1. Correlational (e.g. observational, survey, clinical 2. Experimental B. Statistics 1. Descriptive 2. Inferential C. Ethics in Research 4 Unit II. Methods A. Experimental, Correlational, and Clinical Research Testable Hypotheses Operational Definitions Correlational Relationships “Correlation does not imply causation” Causal Relationships 5 Unit II. Methods A.1. Correlational (e.g. observational, survey, clinical Naturalistic Observation Case Studies Surveys Correlational Research 6 Unit II. Methods Natural Observation Professor Wainwright’s painstaking field research to decode the language of bears comes to a sudden and horrific end 7 Unit II. Methods Natural Observation Naturalistic Observation Exercise by Alan Feldman Students work in teams to observe in public places They observe alone, write up observations, and compare observations later Natural Observation in the Real World by Marissa M. Sarabando Students work in teams to observe in public places They are asked to make a hypothesis of what they expect to observe Share the results in class Hypothesis supported or not? Insight into Negative Correlation 9 Unit II. Methods Experimental & Control Groups 10 Unit II. Methods A.2. Experiments Experimental Design Selection of Participants Population Sample Random sampling Assignment of Participants to Groups Experimental Group Control Group Random Assignment 11 Unit II. Methods Key Ideas in Experiment Design Treatment of Groups Variables Independent Variable (IV) Dependent Variable (DV) Placebo Experimenter Bias (double-blind design) 12 Unit II. Methods Identifying Independent Variables and Dependent Variables Martin Anderson For the following statements create an hypothesis (Your hypothesis should, theoretically, be testable). Then identify the IV and DV. Blondes have more fun. Hypothesis: Changing people’s hair color to blonde will increase the amount of fun that they have. IV ____________________ DV __________________ A rolling stone gathers no moss. Hypothesis: IV ____________________ DV __________________ A researcher is interested in how the activity level of 4-year-olds is affected by viewing Teenage Mutant Ninja Turtles. He shows one group a 30-minute video of Teenage Mutant Ninja Turtles and another group a 30-minute video of Barney. IV:______________DV:_______________ Experimental group:__________________ Control group:_______________________ An Exercise in Designing Research Turn the saying “An apple a day keeps the doctor away” into a hypothesis and design an experiment to test its validity. (This chart can be used to analyze other experiments) Other Ideas for Research Design An Exercise in Designing Research Step One: Form an hypothesis Form an Hypothesis State the relationship you expect to find. Hypothesis The hypothesis needs to be testable. Think in terms of operational definitions. An Exercise in Designing Research Step Two: Pick your subjects Pick Subjects Describe the process you will use to select subjects for your experiment. Subject Selection The population is the group you are studying, Your subjects are a sample from the population. An Exercise in Designing Research Step Three: Assign your subjects to groups Assign Subjects Assignment to Group Describe how you will divide the subjects into the control group and the experimental group. The control group and experimental group should be as similar as possible to each other. An Exercise in Designing Research Step Four: Defining your independent variable Independent Variable Describe your Operational Definition How are you going to measure the IV? Experimental Group Control Group This group “gets” This group the IV. doesn’t “get” the IV. (It might get a placebo, however). An Exercise in Designing Research Step Five: Defining your dependent variable Dependent Variable Expected Result Expected Result Describe your Operational Definition – How are you going to measure the DV? The DV is the same for both groups. You expect a measurable difference between the groups. An Exercise in Designing Research Step Six: Statistical analysis Analysis of Outcomes How are you going to see if the groups are different? (You do not need to identify the exact statistical procedures) Comparison of Groups The statistical analysis gives you an idea if the differences between the two groups are big enough to be greater than chance. Experimenter Bias Possible sources of Experimenter Bias Ways to control for Experimenter Bias. The experimenter may consciously or unconsciously do things that can affect the experiment so that it will confirm the experimenter’s hypothesis. Confounding Variables Possible Confounding Variables Ways to control for Confounding Variables Explain Blind and Double Blind Designs Variables (other than the variables that are being studied) that can have an affect on the outcome of the study. Confounding Variable “When Dr. Henderson comes in, everybody play dead.” Ethical Considerations Describe how ethical considerations will be dealt with in the research. Basic Ethical Principles •Informed Consent (Use of Deception?) •Protection from harm and discomfort •Confidentiality of information about participants •Debriefing participants after the research Flawed Experiment (Source unknown) A psychologist wishes to study the effect of a reinforcement of food on the performance of a fine motor skill involving eye hand coordination. To accomplish this, he had his subjects thread as many needles as possible in a five minute period. The subjects were divided into two groups: Group A Group B Males 20 28 Females 30 22 Total 50 50 The psychologist explained the tests to each group in the same way. However, she offered Group A a voucher for a free lunch for every 20 needles threaded. After the fiveminute time period had expired, he counted the number of needles threaded by each group. Flawed Experiment The results were as follows: Total Number of Needles Threaded Group A 80 Group B 45 Average Number of Needles Threaded per Person 1.8 0.9 From these results, the psychologist concluded that the reward of food caused Group A to thread more needles that Group B. What was the independent variable? What was the dependent variable? Which of the two groups was the control group? Why? Which of the two groups was the experimental group? Why? How could the following variables negate the psychologist’s conclusions? Age of the subjects? Sex of the subjects? B.1. Descriptive Statistics Measures of Central Tendency Mode Median Mean Measures of Variability Range Standard Deviation 28 Unit II. Methods Normal Curve - Normal Distribution 68% Skew – Skewed Distributions Positive Skew Negative Skew 29 Unit II. Methods Creating A Living Frequency Distribution: A Way to Introduce Key Statistical Terms and Concepts Martin Anderson Overview This exercise demonstrates basic statistical concepts. By forming a “living frequency distribution” based on height, students will gain direct, first-hand knowledge of the following terms and the concepts they represent: Variable Discrete, Continuous Nominal Classification Dichotomy / Trichotomy Continuum Measures of Central Tendency Median, Mode, Arithmetic Mean Measures of Variability Range Distribution Histogram, Normal Curve, Skew, Outlier Creating A Living Frequency Distribution (2) Materials Cardboard sheets for signs Marking pen 30’ length of cord (extension cords connected together work well) Create signs labeled with key terms and concepts as follows to give to designated students: Median, Mode (best to make several of these), Range From , Range To Create additional signs to indicate various heights from 4’6” through 6’5”: Time Required This exercise is easily done in one class period. Creating A Living Frequency Distribution (3) Step One: Creating a Dichotomy I ask students to divide into two groups - tall individuals on one side of the room and short individuals on the other Step Two: Creating a Continuum Step Three: Identifying the Median Step Four: Identifying the Range Creating A Living Frequency Distribution (4) Step Five: Identifying the Mode Step Five: Calculating Arithmetic Mean Step Six: Demonstrating Normal Distribution Creating A Living Frequency Distribution (5) Step Seven: Demonstrating Skew Step Seven: Discussion Step Eight: Follow-up A Three-Dimensional Model of the Normal Curve William E. Addison & Kristine R. Hillman A common problem is conceptualizing relationships among areas under the normal curve Students have access to a wooden model of the normal curve. The model consists of a total of six pieces, two each of three different sections. 2 of 34%, 2 of 14%, 2 of 2% The pieces correspond in relative size and shape to approximate areas delineated by standard deviation units in an empirical normal distribution This helps them to visualize the concept of symmetry And how the symmetry of the normal curve relates to concepts such as central tendency, variability, relative standing Normal Distribution Curve Insight into Negative Correlation 37 Unit II. Methods Correlation Coefficients Positive Correlation Negative Correlation Discussion: Ways to explain and demonstrate this to students. 38 Unit II. Methods 2. Inferential Evaluation of chance Probability that results are by chance alone Tests of Significance Determine the likelihood that a specific outcome was obtained by chance alone Importance of Random Assignment 39 Unit II. Methods Is it Representative? Can we Generalize? Sample / Population Replication 40 Unit II. Methods What is “Significance?” Common Usage Important Meaningful etc. Term of Art: Statistical Significance Reliable Repeatable 41 Unit II. Methods Significance Testing Significant Result in Research Not necessarily large or important Not necessarily dramatic But probably did not occur by chance Null Hypothesis Opposite of Hypothesis Hypothesis: Anxiety reduces test performance Null Hypothesis: Anxiety does not effect test performance. Significance Testing (continued) p-level (Probability Level) Probability that your null hypothesis is correct Probability that the statistic is really zero Examples: Difference in means Correlation coefficient p < .05 (p < .01) Your null hypothesis has less than a 5% chance of being right You have less than a 5% chance of being wrong Type I and Type II Errors Type I Error Deciding that one variable has an effect on (or a relationship to) another variable when it doesn’t p-level gives the odds of making this kind of error Type II Error Deciding that one variable does not have an effect on (or a relationship to) another variable when it does There is no easy way to estimate the odds of this kind of error C. Ethics in Research Informed consent Minimize risk and discomfort Potential benefits must outweigh risk to subjects Confidentiality Debriefing Ethics of animal research Approval of research committee 45 Unit II. Methods How Psychologists Do Research Spearman Rank Order Correlation Coefficient We have seven subjects whose art projects are being ranked by two judges, and we wish to know if the two judges rankings are related to one another. In other words, do the two judges tend to rank the seven art show contestants in the same way? The formula for the Spearman Correlation Coefficient is: In which r2 = Spearman Correlation Coefficient ∑ = Sum of D2 = Difference squared N = number of subjects Spearman Rho for Rankings of Two Judges of Art Projects for Seven Subjects subject Judge A Ranking Judge B Ranking D 2 D Alan 1 2 -1 1 Betty 2 1 1 1 Carlos 3 4 -1 1 Diana 4 3 1 1 Edward 5 6 -1 1 Fern 6 7 -1 1 Greg 7 5 2 4 ∑ 10 Thus we can see that there is a high positive correlation, but not a perfect correlation between the two judges ratings.
