1Studying Child Development:The Scientific Method• Treat beliefs about development as hypotheses (educatedguesses) that need to be tested.• Test them using the scientific method:– Choose a question to be answered.– Formulate a hypothesis regarding the question.– Develop a method for testing the hypothesis.– Use the data yielded by the method to draw aconclusion regarding the hypothesis.The Importance of AppropriateMeasurement• Measurements must yield reliable and validresults.– Reliability: Independent measurements of abehavior are consistent with each other.– Validity: The test or experiment measureswhat it is intended to measure.Reliability• Reliability: Consistency of measures– Inter-rater reliability: The amount ofagreement between different observers ortesters. Agreement should be high.– Test–retest reliability: Results should besimilar over repeated testing.Validity• Internal validity: Are the effects observedattributable to conditions the researcherintentionally manipulated?• External validity: Do the conclusions allowgeneralization beyond the particulars of thisexperiment?2Studying Child Development:Contexts for Gathering Data• Interviews– Structured interview: Collecting self-reports from all people beingstudied.– Clinical interview: In-depth focus on each subject.Studying Child Development:Contexts for Gathering Data• Naturalistic observation: Study children in their usualenvironments—home, play, school.Studying Child Development:Contexts for Gathering Data• Structured observation: Research based on studyingchildren engaging in designed tasks or situations,usually in a laboratory.Correlation and Causation• Variables are attributes that vary acrossindividuals and situations.• Behavioral research is concerned withdetermining if and how many of thesevariables are related.• Correlational and experimental designs arethe two main ways of doing this.3Correlational Designs• Correlation is the relationship between twovariables.• Correlations can be either positive or negativein direction.• The direction and strength of a correlation areindicated by a statistic known as thecorrelation coefficient.+ 0.56Correlations—Five VariationsCorrelation vs. Causation• Correlation does not equalcausation.– Correlation does not tell you if one variable causesanother.– There may be a third variable.• Finding causation requires an experiment.Experimental Designs• Experiment can prove causation if the participants aresimilar enough to one another and are tested in samesituation.– Random assignment ensures that comparable researchsubjects submit to same experimental setting.– Experimental control: One group is tested in theexperiment and one group—the control group—is not.4Experimental Control• Independent variable: The experience that theexperimental group is exposed to.• Dependent variable: The behavior that isaffected by exposure to the experiment.Designs for studying development• Cross-sectional - compare children of differentages on a given behavior• Longitudinal - follow group of children oversubstantial period of time• Microgenetic - follow group of childrenclosely as behaviors