Methods In Psychological Research Unit 08

‭Quasi-Experiments‬

‭Methodological Toolbox‬
‭➔‬ ‭construct validity‬‭tool box‬
‭◆‬ ‭manipulation checks‬
‭◆‬ ‭constants‬
‭◆‬ ‭conceptual/operational definitions‬
‭◆‬ ‭instrument accuracy‬
‭➔‬ ‭external validity‬‭tool box‬
‭◆‬ ‭random sampling‬
‭◆‬ ‭ecological validity‬
‭◆‬ ‭experimental realism‬
‭➔‬ ‭statistical validity‬‭tool box‬
‭◆‬ ‭sample size‬
‭◆‬ ‭replicability‬
‭◆‬ ‭effect size‬
‭◆‬ ‭significance‬
‭➔‬ ‭internal validity‬‭tool box‬
‭◆‬ ‭random assignment‬


‭Internal Validity‬
‭➔‬ ‭the‬‭3 conditions‬‭of claiming casualty‬
‭◆‬ ‭covariance:‬‭as one variable changes, so does the other‬
‭◆‬ ‭temporal precedence:‬‭must establish the direction‬‭of causality‬
‭◆‬ ‭internal validity:‬‭no other explanations exists for‬‭the effect (no confounds)‬
‭➔‬ ‭3 ways to establish internal validity‬
‭◆ ‬ ‭comparison groups‬
‭●‬ ‭carefully select or create ‘equal’ comparison groups‬
‭○‬ ‭matching or equating in a non-experimental context‬
‭◆ ‬ ‭temporal precedence‬
‭●‬ ‭study the phenomenon longitudinally‬‭(over time)‬
‭●‬ ‭get a sense of when the IV is introduced and when the DV (post-IV) is‬
‭introduced‬
‭●‬ ‭measure before the IV, during the IV, and after the IV‬
‭◆ ‬ ‭rule out alternative explanations‬
‭●‬ ‭isolate and control for potential confounds‬


‭Review of Terms‬
‭➔‬ ‭IV‬‭: a factor that impacts the DV‬
‭➔‬ ‭mediators‬‭: explain why IV impacts the DV‬

, ‭➔‬ ‭moderators‬‭: explains when the effect occurs (i.e. gender)‬
‭➔‬ ‭intervention‬‭: the treatment or the causal agent‬
‭◆‬ ‭the general IV outcome‬


‭Experiments‬
‭➔‬ ‭the best way to test causality claims‬
‭◆‬ ‭shows covariance by‬‭manipulating conditions‬‭of the‬‭IV‬
‭●‬ ‭comparison groups‬
‭●‬ ‭allows for clearer comparisons of outcomes of the DV‬
‭◆‬ ‭shows temporal precedence by‬‭manipulating IV before‬‭measure the DV‬
‭●‬ ‭establishes directionality of the effect‬
‭◆‬ ‭rules out alternative explanations by‬‭controlling‬‭for them‬
‭●‬ ‭randomly assign participants to conditions‬
‭○‬ ‭best way to create unbiased groups for comparison‬
‭●‬ ‭holding all factors constant expect for the IV‬
‭○‬ ‭reduces confounds and helps in isolating cause-and-effect‬
‭➔‬ ‭not always possible or ideal‬
‭◆‬ ‭logistically‬‭- may not be possible to randomly assign‬‭participants to conditions‬
‭●‬ ‭i.e. does smoking cause cancer?‬‭can’t randomly assign‬‭participants to smoke to‬
‭create a condition group‬
‭◆‬ ‭ethically‬‭- some questions can’t be ethically addressed‬‭with an experimental study‬
‭●‬ ‭i.e. are smartphones ruining our relationships?‬‭digging‬‭into people’s personal‬
‭relationships and could cause harm to those relationship‬
‭◆‬ ‭generalizability‬‭- desire to examine phenomenon in‬‭a less controlled, more real-world‬
‭context‬
‭●‬ ‭i.e. what are the effects of social isolation?‬‭can’t‬‭mimic social isolation and assume‬
‭the effects will be the same‬


‭Quasi-Experiments‬
‭➔‬ ‭digs deeper into “why” something occurs‬
‭➔‬ ‭the bridge between correlation studies and true experiments‬
‭➔‬ ‭attempts to establish the three conditions of casualty in ways other than true experiments‬
‭◆‬ ‭covariance‬‭: carefully selects comparison groups‬
‭◆‬ ‭temporal precedence‬‭: study the phenomenon over time‬
‭◆‬ ‭internal validity‬‭: isolate and control for alternative‬‭explanations‬
‭●‬ ‭can only control for‬‭known‬‭confounds‬

‭Worst to Best Design‬
‭➔‬ ‭one-group design‬
‭◆‬ ‭introduce a treatment within one group of participants and measure the outcomes‬
‭◆‬ ‭the worst design because doesn’t include comparison group‬