# research methods in psychology strategies statistics & ethics

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Research Methods in PsychologyStrategiesStatistics& Ethics

Research Strategies

Research StrategiesExperimentResearcher changes one or more factors to observe their effect on some behavior or mental process DOES IDENTIFY CAUSE/EFFECT RELATIONSHIPSampling errors, placebo effect, not natural environment could alter true effect

Research StrategiesCase Study (descriptive)in depth fact finding on a single subjectIntensive, specific infoNo cause/effect; lots of time; no generalizationNaturalistic Observation (descriptive)Observation in natural/real setting without changing environmentGathers naturally occurring data; real worldObserver bias; no cause/effect

Research StrategiesSurvey Research (descriptive)Collect data through interviews questionnaires{but beware of:}false consensus effectbad sampling (especially self-selection!!!)Reduces validity and reliability = wording effects

Research StrategiesCorrelational studies (descriptive)Examines the degree* of relationship between two variablesStudy real world connectionsNO cause/effect just CONNECTION*degree of relationship just means how much they correlate.

Research StrategiesOne last note about correlational studies:

If you HAVE to get a tattoo, then I suggest the following:

Correlation is not causation.

Research StrategiesIf marbles of two colors are mixed well in the large jar, the fastest way to know their ratio is to blindly transfer a few into a smaller one and count them

Research StrategiesPopulationall the cases in a group, from which samples may be drawn for a studyRandom Samplea sample that fairly represents a population because each member has an equal chance of inclusionStratified random samples

Experiments (cont)Three Possible Cause-Effect Relationships(1)Low self-esteemDepression(2)DepressionLow self-esteemLow self-esteemDepression(3)Distressing eventsor biologicalpredispositioncould causecould causecould causeororand

ControlsSingle & Double-blind ProceduresSubjects (or both the subjects and the research staff )are ignorant (blind) about whether the subject has received the treatment or a placebocommonly used in drug-evaluation studiesPlacebo an inert substance or condition that may be administered instead of a presumed active agent, such as a drug, to see if it triggers the effects believed to characterize the active agent

ControlsRandom Assignmentassigning subjects to experimental and control conditions by chanceminimizes pre-existing differences between those assigned to the different groups

ControlsExperimental Conditionthe condition of an experiment that exposes subjects to the treatment, that is, to one version of the independent variableControl Conditionthe condition of an experiment that contrasts with the experimental treatment serves as a comparison for evaluating the effect of the treatment

ControlsIndependent Variable the hypothesized cause of a phenomenontypically manipulated by experimenterDependent Variable the hypothesized effect in a phenomenonin psychology it is usually a behavior or mental process measured by the experimenter

ControlsSo how do you control for the big daddy of confounds, Chance?Random assignment to conditions PLUSInferential statistics

Research StrategiesComparing Research MethodsResearch Method Basic Purpose How Conducted What is ManipulatedDescriptive - To observe and Case studies, surveys, NothingOne variable at record behavior and naturalistica time observationsDescriptive - To detect naturally Computing correlationsNothingTwo variables occuring relationship , sometimesat a time to assess how wellamong survey one variable predictsresponsesExperimental To explore causeManipulating one orIndependent and effectmore factors and usingvariable(s)random assignmentto eliminate preexistingdifferences among subjects

StatisticsStatistics come in two basic flavors:Descriptive (duh.)Inferential : did my observed result REALLY happen, or was it just by chance?

Descriptive stats tell you 3 basic things:Central tendencyVariabilityCorrelation

Modethe most frequently occurring score in a distributionMeanthe arithmetic average of a distributionobtained by adding the scores and then dividing by the number of scoresMedianthe middle score in a distributionhalf the scores are above it and half are below itMathematical Tools-- Central Tendency --

Rangethe difference between the highest and lowest scores in a distributionStandard Deviationa computed measure of how much scores vary around the meanStatistical Significancea statistical statement of how likely it is that an obtained result occurred by chanceMathematical Tools-- Variation --

Mathematical Tools-- Covariation --Correlation Coefficienta statistical measure of the extent to which two factors vary together and thus how well either factor predicts the other

Correlation coefficientIndicates directionof relationship(positive or negative)Indicates strengthof relationship(0.00 to 1.00)r = +.37

Mathematical Tools

Mathematical Toolsaka Statistical ReasoningScatterplota graphed cluster of dots, each of which represents the values of two variablesthe slope of the points suggests the direction of the relationshipthe amount of scatter suggests the strength of the correlationlittle scatter indicates high correlationalso called a scattergram or scatter diagram

Mathematical ToolsScatterplot of Height and Temperament55 60 65 70 75 80 85

Mathematical Tools

Mathematical Tools:Inferential statisticsSOLE purpose: is this result due to chance or not?Typically assessed with a probability value or p-valueCut off is usually .05 (but theres nothing magical about that number!)P-values are NOT measures of effect sizeEffect size is always more important.

Statistical trapsMistaking correlation for causationthe perception of a relationship where none exists(re: availability)

Statistical trapsRandom SequencesYour chances of being dealt either of these hands is precisely the same: 1 in 2,598,960.

Statistical trapsCheating with graphs:

Statistical trapsCheating with graphs

Statistical trapsWhich mean is which?A Skewed Distribution

Worlds fastest ethics lectureDoing research with humans basic principles:Rights & well-being of participants outweigh the benefits of the research

Participants have to be allowed to decide to participate or not: Informed Consent is the cornerstone of ethical research.

Worlds fastest ethics lectureParticipants have the right to withdraw from the study at any time, without penalty.

Participants must be protected from risks or informed of risks that cant be removed. Risk/benefit ratio must be positive.

Deception is avoided whenever possible and must be justified if it is used.

Worlds fastest ethics lectureResearchers have the duty to inform the participants of the true purpose of the study (usually done in the debriefing)

Data must remain confidential and secure (trickier these days with computers!)

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