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Unit II. Methods4
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
A. Experimental, Correlational, and Clinical Research
Unit II. Methods5
Testable Hypotheses Operational Definitions Correlational Relationships
“Correlation does not imply causation”
Causal Relationships
A.1. Correlational (e.g. observational, survey,
clinical
Unit II. Methods6
Naturalistic ObservationCase StudiesSurveys Correlational Research
Natural Observation
Professor Wainwright’s painstaking field research to decode the language of bears comes to a sudden and horrific end
Unit II. Methods7
Natural ObservationNaturalistic Observation Exercise
by Alan FeldmanStudents work in teams to observe in public
placesThey observe alone, write up observations,
and compare observations later
Natural Observation in the Real Worldby Marissa M. SarabandoStudents work in teams to observe in public
placesThey are asked to make a hypothesis of what
they expect to observe Share the results in classHypothesis supported or not?
A.2. Experiments
Unit II. Methods11
Experimental DesignSelection of Participants
PopulationSampleRandom sampling
Assignment of Participants to GroupsExperimental GroupControl GroupRandom Assignment
Key Ideas in Experiment Design
Unit II. Methods12
Treatment of GroupsVariables
Independent Variable (IV) Dependent Variable (DV)
PlaceboExperimenter Bias (double-blind
design)
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
Hypothesis
State the relationship you expect to find.
The hypothesis needs to be testable. Think in terms of operational definitions.
An Exercise in Designing ResearchStep Two: Pick your subjects
Pick Subjects Subject Selection
Describe the process you will use to select subjects for your experiment.
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
Experimental Group
Control Group
Describe your Operational Definition - How are you going to measure the IV?
This group “gets” the IV.
This group 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 Comparison of Groups
How are you going to see if the groups are different?(You do not need to identify the exact statistical procedures)
The statistical analysis gives you an idea if the differences between the two groups are big enough to be greater than chance.
Experimenter Bias
The experimenter may consciously or unconsciously
do things that can affectthe experiment so that it will confirm the experimenter’s
hypothesis.
Possible sources of
Experimenter Bias
Ways to control for
Experimenter Bias.
Confounding Variables Variables (other than the variables that are being
studied)that can have an affect on the outcome of the study.
Possible Confounding Variables
Ways to control for Confounding
Variables
Explain Blind and Double Blind
Designs
Ethical Considerations
Basic Ethical Principles
•Informed Consent (Use of Deception?)
•Protection from harm and discomfort
•Confidentiality of information about participants
•Debriefing participants after the research
Describe how ethical considerations will be
dealt with in 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: Males Females TotalGroup A 20 30 50Group B 28 22 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 five-minute 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 Average Number of Needles Threaded Threaded per Person Group A 80 1.8 Group B 45 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
Unit II. Methods28
Measures of Central TendencyModeMedianMean
Measures of VariabilityRangeStandard Deviation
Unit II. Methods29
Normal Curve - Normal Distribution68%
Skew – Skewed DistributionsPositive SkewNegative Skew
Creating A Living Frequency Distribution:A Way to Introduce Key Statistical Terms and ConceptsMartin 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)
MaterialsCardboard sheets for signsMarking pen30’ 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 ToCreate 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 DichotomyI 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 MeanStep Six: Demonstrating Normal
Distribution
Creating A Living Frequency Distribution (5)
Step Seven: Demonstrating SkewStep Seven: DiscussionStep Eight: Follow-up
A Three-Dimensional Model of the Normal CurveWilliam 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
Unit II. Methods38
Correlation CoefficientsPositive CorrelationNegative Correlation
Discussion: Ways to explain and demonstrate this to students.
2. Inferential
Unit II. Methods39
Evaluation of chance Probability that results are by chance alone
Tests of SignificanceDetermine the likelihood that a specific outcome was obtained by chance alone
Importance of Random Assignment
Unit II. Methods41
What is “Significance?”Common Usage
ImportantMeaningfuletc.
Term of Art: Statistical Significance ReliableRepeatable
Significance TestingSignificant Result in Research
Not necessarily large or importantNot necessarily dramaticBut probably did not occur by chance
Null HypothesisOpposite 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
correctProbability that the statistic is really zero
Examples:Difference in meansCorrelation coefficient
p < .05 (p < .01)Your null hypothesis has less than a 5%
chance of being rightYou have less than a 5% chance of being
wrong
Type I and Type II Errors
Type I ErrorDeciding 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 ErrorDeciding 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
Unit II. Methods45
Informed consentMinimize risk and discomfort
Potential benefits must outweigh risk to subjects
Confidentiality DebriefingEthics of animal researchApproval of research committee
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 D2
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