Total = 21 slides1Sociology 201:Social Research Design17. Experiments IITotal = 21 slides2Preview•Review homework•Solomon Four-Group Design•External InvalidityTotal = 21 slides3Review Workbook assignment•Range: 15 - 200•Two have 200***•150-197: 10 •100 - 149: 16•15-99: 12• 195 points remaining–Everybody can playTotal = 21 slides48.2 - Conducting an experiment• Different forms of greeting• Share about the experience of doing the experiment.Total = 21 slides5The Classical ExperimentPre-test Post-testStimulus(DV) (DV)(IV)ExperimentalControlGroupGroupThe problem with this is that the pre-test may cause the internal invalidity problem of testing.How could we solve this problem?Total = 21 slides6Solomon Four-Group DesignPre-test Post-testStimulus(DV) (DV)(IV)ExperimentalControlGroupGroupExperimentalControlGroupGroupLet’s assume DV is prejudiceTotal = 21 slides7Solomon Four-Group Design: ComparisonPre-test Post-testStimulus(DV) (DV)(IV)ExperimentalControlGroupGroupExperimentalControlGroupGroupPost-test should show less prejudiceTotal = 21 slides8Solomon Four-Group Design: ComparisonPre-test Post-testStimulus(DV) (DV)(IV)ExperimentalControlGroupGroupExperimentalControlGroupGroupPost-test should show same prejudiceTotal = 21 slides9Solomon Four-Group Design: ComparisonPre-test Post-testStimulus(DV) (DV)(IV)ExperimentalControlGroupGroupExperimentalControlGroupGroupExperimental groups should have less prejudiceTotal = 21 slides10Solomon Four-Group Design: ComparisonPre-test Post-testStimulus(DV) (DV)(IV)ExperimentalControlGroupGroupExperimentalControlGroupGroupThese would determine effects of testingTotal = 21 slides11Problems of External Invalidity• Generalizability of the observed effects•Effects might not be produced in real worldTotal = 21 slides12Interaction of Selection and Treatment–Generalize beyond the kind of people studied?–Maybe giving computers to high school students would work, but not adultsTotal = 21 slides13Interaction between Testing Situation and Treatment–Maybe the computers only produce the effect when subjects under scrutiny–Putting computers in community associations might not help high school studentsTotal = 21 slides14Interaction of History and Treatment•Would historical events disrupt the cause/effect?•Maybe computers will come to be seen as the tool of the devilTotal = 21 slides15Natural ExperimentsTotal = 21 slides16Natural Experiments: BombingTotal = 21 slides17Natural Experiments: MeltdownThree-Mile Island (1979)Total = 21 slides18Natural Experiments: Roots•Miniseries on African-American history (1976-79)•Did it affect racial attitudes?•How would you design a natural experiment?Total = 21 slides19Preview Workbook Assignments••9.2 Doing a Survey –Be sure to interview people–Not self-administeredTotal = 21 slides20Next Time•Survey Research I•Read Chapter