the need for psychological science psychologists, like all scientists, use the scientific method to...
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The Need for Psychological The Need for Psychological ScienceScience
Psychologists, like all scientists, Psychologists, like all scientists, use the scientific method to use the scientific method to
construct theories that construct theories that organize observations and organize observations and imply testable hypothesesimply testable hypotheses
The Need for Psychological The Need for Psychological ScienceScience
Hindsight BiasHindsight Bias we tend to believe, after learning an we tend to believe, after learning an
outcome, that we would have outcome, that we would have foreseen it foreseen it
the “I-knew-it-all-along” phenomenonthe “I-knew-it-all-along” phenomenon
OverconfidenceOverconfidence we tend to think we know more than we tend to think we know more than
we dowe do
The Need for The Need for Psychological SciencePsychological Science
The biases and errors of people’s The biases and errors of people’s everyday judgments illustrate the everyday judgments illustrate the need for:need for:
1.1. SkepticismSkepticism
2.2. HumilityHumility
3.3. Critical ThinkingCritical Thinking
The Need for Psychological The Need for Psychological ScienceScience
Critical ThinkingCritical Thinking thinking that does thinking that does
not blindly accept not blindly accept arguments and arguments and conclusionsconclusionsexamines examines
assumptionsassumptionsdiscerns hidden discerns hidden
valuesvaluesevaluates evidenceevaluates evidence
The Amazing Randi--Skeptic
Goals of Psychology
Describe Explain Predict Control
behavior and mental processes
Scientific Method Formulate testable questions
Develop hypotheses Design study to collect data
Experimental Descriptive
Analyze data to arrive at conclusions Use of statistical procedures Use of meta-analysis
Report results Publication Replication
The Need for Psychological The Need for Psychological ScienceScience
Experimentation
DescriptionDescription
Psychologists describe Psychologists describe behavior using case studies, behavior using case studies, surveys, surveys,
and naturalistic observationand naturalistic observation
Defined as a thorough, exhaustive study of a person. It includes personal, educational, family and work histories.Advantage:
A wealth of background information about one person
Disadvantages:Information cannot be generalized to others; also, researcher’s biases can influence subject’s behavior.
The Case Study Method
DescriptionDescription
Case StudyCase Study Psychologists Psychologists
study one or study one or more more individuals in individuals in great depth in great depth in the hope of the hope of revealing revealing things true of things true of us allus all Is language uniquely human?
The Survey Method
Defined as asking questions of a carefully selected group of people and tabulating their answers.
Information can be gathered about feelings, opinions, and behavior patterns.
Interpretation difficult; sample may not be representative.
Advantage:
Disadvantages:
DescriptionDescription
SurveySurvey technique for ascertaining the self-technique for ascertaining the self-
reported attitudes or behaviors of peoplereported attitudes or behaviors of people usually by questioning a representative, usually by questioning a representative,
random sample of peoplerandom sample of people
Wording EffectsWording Effects Even subtle changes in the order or Even subtle changes in the order or
wording of questions can have major wording of questions can have major effects.effects.
Samples and SamplingSamples and Sampling
• SampleSampleselected segment of the populationselected segment of the population
• Representative sampleRepresentative sampleclosely parallels the population on closely parallels the population on relevant characteristicsrelevant characteristics
• Random selectionRandom selectionevery member of larger group has equalevery member of larger group has equal change of being selected for the study change of being selected for the study samplesample
Evaluating Media ReportsEvaluating Media Reports• Be skeptical of sensationalist claimsBe skeptical of sensationalist claims
• Goal of “shock” media is ratingsGoal of “shock” media is ratings
• Look for original sourcesLook for original sources
• Separate opinion from dataSeparate opinion from data
• Consider methodology and Consider methodology and operational definitionsoperational definitions
• Correlation is not causalityCorrelation is not causality
• Skepticism is the rule in science.Skepticism is the rule in science.
DescriptionDescription
DescriptionDescription
If marbles of two If marbles of two colors are mixed colors are mixed well in the large well in the large jar, the fastest way jar, the fastest way to know their ratio to know their ratio is to blindly is to blindly transfer a few into transfer a few into a smaller one and a smaller one and count themcount them
DescriptionDescription
Naturalistic Naturalistic ObservationObservation observing and observing and
recording behavior recording behavior in naturally in naturally occurring situations occurring situations without trying to without trying to manipulate and manipulate and control the situationcontrol the situation
The Naturalistic Observation Method
Defined as observing behaviors in their natural settings.
Disadvantages:Researcher cannot interact with the subject.
Researcher may interpret subject’s responses incorrectly.
DescriptionDescription
False Consensus EffectFalse Consensus Effect tendency to overestimate the extent tendency to overestimate the extent
to which others share our beliefs and to which others share our beliefs and behaviorsbehaviors
PopulationPopulation all the cases in a group, from which all the cases in a group, from which
samples may be drawn for a studysamples may be drawn for a study
CorrelationCorrelation Correlation CoefficientCorrelation Coefficient
a statistical measure of the extent to which two factors a statistical measure of the extent to which two factors vary together, and thus how well either factor predicts vary together, and thus how well either factor predicts the otherthe other
Correlation coefficient
Indicates directionof relationship
(positive or negative)
Indicates strengthof relationship(0.00 to 1.00)
r = +.37
Coefficient of CorrelationCoefficient of Correlation
Numerical indication of magnitude Numerical indication of magnitude and direction of the relationship and direction of the relationship between two variablesbetween two variables– Positive correlationPositive correlation— two variables — two variables
vary systematically in the SAME vary systematically in the SAME directiondirection
– Negative correlationNegative correlation— two — two variables vary systematically in variables vary systematically in OPPOSITE directionsOPPOSITE directions
Correlation
Perfect positivecorrelation (+1.00)
No relationship (0.00) Perfect negativecorrelation (-1.00)
Scatterplots, showing patterns of correlations
CorrelationCorrelationScatterplotScatterplot--- a graphed cluster of dots, each of - a graphed cluster of dots, each of
which represents the values of two variables. The which represents the values of two variables. The slope of the points suggests the degree and slope of the points suggests the degree and direction of the relationship between the two direction of the relationship between the two variables.variables.
Correlation CoefficientCorrelation Coefficient---- a statistical measure of a statistical measure of how strongly related any two sets of scores are. It how strongly related any two sets of scores are. It can range from can range from +1.00 (a perfect correlation) +1.00 (a perfect correlation) through 0.00 (the scores are unrelated) to -through 0.00 (the scores are unrelated) to -1.00 (a perfect negative correlation).1.00 (a perfect negative correlation). Scores Scores with a positive correlation increase and decrease with a positive correlation increase and decrease together. A negative correlation coefficient together. A negative correlation coefficient indicates that one score falls as the other rises. indicates that one score falls as the other rises.
Regression toward the meanRegression toward the mean—— falling back to falling back to the norm. It can fuel the illusion that the norm. It can fuel the illusion that uncontrollable events correlate with out actions.uncontrollable events correlate with out actions.
CorrelationCorrelation
ScatterplotScatterplot a graphed cluster of dots, each of which a graphed cluster of dots, each of which
represents the values of two variablesrepresents the values of two variables the slope of the points suggests the the slope of the points suggests the
direction of the relationshipdirection of the relationship the amount of scatter suggests the the amount of scatter suggests the
strength of the correlationstrength of the correlation little scatter indicates high correlationlittle scatter indicates high correlation
also called a scattergram or scatter also called a scattergram or scatter diagramdiagram
CorrelationThree Possible Cause-Effect Relationships
(1)Low self-esteem
Depression
(2)Depression
Low self-esteem
Low self-esteem
Depression
(3)Distressing events
or biologicalpredisposition
could cause
could cause
could cause
or
or
and
Correlation
Scatterplot of Height and Temperament
55 60 65 70 75 80 85
959085807570656055504540353025
Temperamentscores
Height in inches
CorrelationHeight and Temperament of 20 Men
123456789
10
11121314151617181920
80636179746962757760
64767166737063716870
75666090604242608139
48697257637530578439
SubjectHeight in
Inches Temperament SubjectHeight in
Inches Temperament
Illusory CorrelationIllusory Correlation
Illusory Illusory CorrelationCorrelation the the
perception of perception of a relationship a relationship where none where none existsexists
Conceive Do not conceive
Adopt
Do notadopt
disconfirming evidence
confirming evidence
disconfirming evidence
confirming evidence
Two Random SequencesTwo Random Sequences
Your chances Your chances of being dealt of being dealt either of either of these hands is these hands is precisely the precisely the same: 1 in same: 1 in 2,598,960.2,598,960.
ExperimentationExperimentation
Experiment Experiment an investigator manipulates one or an investigator manipulates one or
more factors (independent variables) more factors (independent variables) to observe their effect on some to observe their effect on some behavior or mental process (the behavior or mental process (the dependent variable) dependent variable)
by random assignment of participants by random assignment of participants the experiment controls other the experiment controls other relevant factorsrelevant factors
The Need for Psychological The Need for Psychological ScienceScience
TheoryTheory an explanation using an integrated an explanation using an integrated
set of principles that organizes and set of principles that organizes and predicts observationspredicts observations
HypothesisHypothesis a testable predictiona testable prediction often implied by a theoryoften implied by a theory
X amount of sleeping pills helps the healthy person with insomnia to sleep better.
Sleeping pills
Experimental Group
# of people whohad restful nights
PlacebosIndependent Variable
Groups
Dependent Variable # of people who had restful nights
The hypothesis proves to be incorrect. People taking the sleeping pill over a period of days had more insomnia than before. They had less restful sleep than the people in the control group.
Hypothesis
ControlGroup
The Need for Psychological The Need for Psychological ScienceScience
Operational DefinitionOperational Definition a statement of procedures (operations) a statement of procedures (operations)
used to define research variablesused to define research variables Example-Example-
intelligence may be operationally defined intelligence may be operationally defined as what an intelligence test measuresas what an intelligence test measures
Testing the effects of vitamin C on the Testing the effects of vitamin C on the health of students could be measured by health of students could be measured by the number of colds experienced during the number of colds experienced during the month.the month.
ExperimentationExperimentation
Independent VariableIndependent Variable the experimental factor that is the experimental factor that is
manipulatedmanipulated the variable whose effect is being studiedthe variable whose effect is being studied
Dependent VariableDependent Variable the experimental factor that may change the experimental factor that may change
in response to manipulations of the in response to manipulations of the independent variable independent variable
in psychology it is usually a behavior or in psychology it is usually a behavior or mental process mental process
Experimental DesignExperimental Design
• Random sampleRandom sample— — every member of the every member of the population being studied should have an population being studied should have an equal chance of being selected for the studyequal chance of being selected for the study
• Random assignmentRandom assignment— — assigning assigning subjects to experimental and control subjects to experimental and control conditions by chance. conditions by chance.
• Randomization helps avoid false Randomization helps avoid false resultsresults
ExperimentationExperimentation
PlaceboPlacebo an inert substance or condition that may be an inert substance or condition that may be
administered instead of a presumed active administered instead of a presumed active agent, such as a drug, to see if it triggers agent, such as a drug, to see if it triggers the effects believed to characterize the the effects believed to characterize the active agentactive agent
Double-blind ProcedureDouble-blind Procedure both the research participants and the both the research participants and the
research staff are ignorant (blind) about research staff are ignorant (blind) about whether the research participants have whether the research participants have received the treatment or a placeboreceived the treatment or a placebo
commonly used in drug-evaluation studiescommonly used in drug-evaluation studies
ExperimentationExperimentation
Experimental ConditionExperimental Condition the condition of an experiment that the condition of an experiment that
exposes participants to the treatment, that exposes participants to the treatment, that is, to one version of the independent is, to one version of the independent variablevariable
Control ConditionControl Condition the condition of an experiment that the condition of an experiment that
contrasts with the experimental treatment contrasts with the experimental treatment serves as a comparison for evaluating the serves as a comparison for evaluating the
effect of the treatmenteffect of the treatment
Basic Ethical Guidelines for Psychological Researchers
Do no harm.Accurately describe risks to potential subjects.Ensure that participation is voluntary.Minimize any discomfort to participants.Maintain confidentiality.Do not unnecessarily invade privacy.Remove any misconceptions caused by deception
(debrief).Provide results and interpretations to participants.Treat participants with dignity and respect.
The Need for Psychological The Need for Psychological ScienceScience
ReplicationReplication repeating the essence of a repeating the essence of a
research study to see whether research study to see whether the basic finding generalizes to the basic finding generalizes to other participants and other participants and circumstancescircumstances
usually with different participants usually with different participants in different situationsin different situations
Research StrategiesResearch Strategies
Design of Design of the the subliminal subliminal tapes tapes experimentexperiment
Subliminal tape content
Self-esteem Memory
Memory
Self-esteem
Tape label
DistributionsDistributions
Percentile RankPercentile Rank---the percentage of -the percentage of scores that fall below a particular scores that fall below a particular score. You can never have a percentile score. You can never have a percentile rank of 100 because you are part of rank of 100 because you are part of that 100. (You can’t exceed yourself!)that 100. (You can’t exceed yourself!)
Bar Graphs (histograms)--Bar Graphs (histograms)-- Percentile ranks and distributions can be Percentile ranks and distributions can be represented in bar graphs or histograms.represented in bar graphs or histograms.
Frequency DistributionFrequency Distribution
Frequency Distributions• 1. What are they?
– Tables– Graphs
• Bar• Histogram
HistogramHistogram
Statistical ReasoningStatistical Reasoning
Our Brand Brand BrandBrand X Y Z
100%
99
98
97
96
95
Percentagestill functioningafter 10 years
Brand of truck
Statistical ReasoningStatistical Reasoning
Our Brand Brand Brand Brand X Y Z
100%
90
80
70
60
50
40
30
20
10
0
Percentagestill functioningafter 10 years
Brand of truck
Statistical ReasoningStatistical Reasoning
ModeMode the most frequently occurring score in a the most frequently occurring score in a
distributiondistribution
MeanMean the arithmetic average of a distributionthe arithmetic average of a distribution obtained by adding the scores and then obtained by adding the scores and then
dividing by the number of scoresdividing by the number of scores
MedianMedian the middle score in a distributionthe middle score in a distribution half the scores are above it and half are half the scores are above it and half are
below itbelow it
MedianMedian
• Separates the upper and low half of Separates the upper and low half of distributiondistribution
1) mean and median not necessarily 1) mean and median not necessarily equalequal
2) median much less sensitive to 2) median much less sensitive to extremesextremes
ModeMode
• • Most common valueMost common value
• • Always present in the distributionAlways present in the distribution
• • May be more than one modeMay be more than one mode
• • Used mainly with nominal dataUsed mainly with nominal data
• • Plays minor role in statistical Plays minor role in statistical inferenceinference
Statistical ReasoningStatistical Reasoning
A Positively Skewed DistributionA Positively Skewed Distribution
15 20 25 30 35 40 45 50 90 475 710
70
Mode Median Mean
One Family Income per family in thousands of dollars
Skewed DistributionsSkewed Distributions
PositiveMean > Median
NegativeMean < Median
Statistical ReasoningStatistical Reasoning
RangeRange the difference between the highest and the difference between the highest and
lowest scores in a distributionlowest scores in a distribution Standard DeviationStandard Deviation
a computed measure of how much scores a computed measure of how much scores vary around the meanvary around the mean
Statistical SignificanceStatistical Significance a statistical statement of how likely it is that a statistical statement of how likely it is that
an obtained result occurred by chancean obtained result occurred by chance
VariationVariation
• Normal CurveNormal Curve---a bell-shaped curve -a bell-shaped curve that describes the normal distribution that describes the normal distribution of many types of data. Most scores of many types of data. Most scores fall near the mean and fewer and fall near the mean and fewer and fewer fall near the extremes. fewer fall near the extremes. In a In a normal curve the mean, median and normal curve the mean, median and mode are all near the middle.mode are all near the middle.
Statistical InferenceStatistical Inference
When is it safe to generalize from a When is it safe to generalize from a sample?sample?
1.1.Representative Samples are better than biased Representative Samples are better than biased samples.samples.
2.2.Less-variable observations are more reliable Less-variable observations are more reliable than those that are more variable.than those that are more variable.
3.3.More cases are better than fewer. Larger More cases are better than fewer. Larger samples are better than smaller ones.samples are better than smaller ones.
4.4.As the size of a sample increases, the size of As the size of a sample increases, the size of the standard deviation is most likely to the standard deviation is most likely to decreasedecrease
When is a difference When is a difference significant?significant?
When sample averages are reliable When sample averages are reliable and the difference between them is and the difference between them is large we say the difference has large we say the difference has statistical significancestatistical significance (it reflects a (it reflects a real difference not due to chance or real difference not due to chance or variation between samples).variation between samples).
Longitudinal studiesLongitudinal studies
Frequently Asked Questions Frequently Asked Questions about Psychologyabout Psychology
Is psychology Is psychology free of value free of value judgments?judgments?
*Topic of *Topic of investigationinvestigation
*Research *Research methodsmethods
*Explanatory *Explanatory theoriestheories
Frequently Asked Questions Frequently Asked Questions about Psychologyabout Psychology
Can laboratory Can laboratory experiments illuminate experiments illuminate everyday life?everyday life?
Frequently Asked Questions Frequently Asked Questions about Psychologyabout Psychology
Does behavior depend Does behavior depend on ones culture?on ones culture? Culture--Culture--the enduring the enduring
behaviors, ideas, attitudes, and behaviors, ideas, attitudes, and traditions shared by a large traditions shared by a large group of people and group of people and transmitted from one transmitted from one generation to the nextgeneration to the next
Frequently Asked Questions Frequently Asked Questions about Psychologyabout Psychology
Does behavior vary with Does behavior vary with gender?gender?Psychologists report gender Psychologists report gender differences in our risk of:differences in our risk of:
1.1. AlcoholismAlcoholism
2.2. DepressionDepression
3.3. Eating disordersEating disorders
Frequently Asked Questions Frequently Asked Questions about Psychologyabout Psychology
Why do psychologists study animals?Why do psychologists study animals?
Is it ethical to experiment on animals?Is it ethical to experiment on animals?
Coile & Miller’s analysis of animal research Coile & Miller’s analysis of animal research revealed that psychologists DID NOT:revealed that psychologists DID NOT:
1.1.Shock animals with extremely painful Shock animals with extremely painful shocks that caused them to dieshocks that caused them to die
2.2.Allow animals to die slowly from hunger Allow animals to die slowly from hunger and thirstand thirst
3.3.Place animals in isolation chambers until Place animals in isolation chambers until they were driven insanethey were driven insane
Ethical GuidelinesEthical Guidelines
Is it ethical to experiment on Is it ethical to experiment on people?people?
• Informed consent and voluntary Informed consent and voluntary participationparticipation
• Students as participantsStudents as participants
• Use of deceptionUse of deception
• Confidentiality of recordsConfidentiality of records
• Information about the study and debriefingInformation about the study and debriefing
Frequently Asked Questions Frequently Asked Questions about Psychologyabout Psychology
Is psychology Is psychology potentially dangerous?potentially dangerous?
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