the need for psychological science psychologists, like all scientists, use the scientific method to...

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


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


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

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


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:


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.


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


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.


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


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


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.


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


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


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.


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


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


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


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


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


Can laboratory Can laboratory experiments illuminate experiments illuminate everyday life?everyday life?


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


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


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


Is psychology Is psychology potentially dangerous?potentially dangerous?

the need for psychological science psychologists, like all scientists, use the scientific method to...

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study sample slide

skeptic slide

psychological science

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critical thinking slide

naturalistic observation

case study method

random sample of people