Bransford & Johnson
INDEPENDENT SAMPLES DESIGNS
Lab 5
Bransford & Johnson (1972)
¨ The amount of information we remember varies. What causes this variability?
¨ Theory: people integrate incoming information with prior knowledge ¤ Having context for new information causes us to better
understand and remember it
Lab 5 on Monday
¨ Flipped a coin. Why? ¤ Random assignment to one of two groups
¨ Experimenter manipulated a variable. How? ¤ Treatment group given context for subsequent passage:
“Doing laundry”; control group given no context
¨ Both groups heard 12 sentences, read aloud ¤ Vaguely described process of doing laundry
¨ Experimenter measured 2 dependent variables ¤ Comprehension of passage (rated from 1 to 7) ¤ Sentences recalled from passage (memory)
Lab 5 on Monday
¨ Error variance ¤ What factors could affect comprehension & recall?
n Some people didn’t try; were sleepy; have good (or bad) memory; already heard of this experiment; couldn’t hear the passage well
n What can help make sure this “noise” affects both groups similarly?
n Random assignment(!) helps even out these factors
Lab 5 on Monday
¨ Systematic variance ¤ Treatment variance?
n Context vs. no context
¤ Confound variance? n Both groups heard same passage at same time, in same
setting n Experimental control: no systematic extraneous diffs between
groups
Lab 5 on Monday
¨ Demand characteristics ¤ Why didn’t I tell you all this before the experiment (or
have you read the related article beforehand)? n If you knew the study/prediction, maybe you would have
behaved differently
¨ Experimenter Expectancy effects ¤ Did I enter the data as accurately, objectively as I
could? n Maybe I should have had my T.A. enter the data
Lab 5
¨ Bransford and Johnson (1972) ¤ Context affects comprehension and memory
¨ Our study… ¤ Hypotheses
n Context group will comprehend and recall the passage better than the no context group
n For comprehension n H1: µ context > µ no context n H0: µ context ≤ µ no context
n For recall n H1: µ context > µ no context n H0: µ context ≤ µ no context
Lab 5
¨ Bransford and Johnson (1972) ¤ Context affects comprehension and memory
¨ Our study… ¤ Independent groups/samples
n 2 groups: context vs. no context n Random assignment to group (or level/condition) n Evaluate differences between groups using t-test for
independent groups n 2 x (one t-test for each dependent variable)
Lab 5
¨ Title Page ¨ Abstract ¨ Introduction ¨ Method ¨ Results ¨ Discussion ¨ References ¨ Figures/Tables
Lab 4 Title Page
¨ Title Page ¤ You’ve got this by
now…
Lab 5 Results: Step-by-step
¨ Write the question the analysis will answer ¨ Write the analysis, including variables analyzed ¨ Write the result of the analysis
¤ INCLUDE MEANS and STANDARD DEVIATIONS for each group, for each DV n “The context group (M = ____, SD = _____) rated comprehension as
higher than the no-context group (M = ____, SD _____).” n An independent samples t-test confirmed that this difference was
significant, t(__) = ___, p = ___. n DO THIS FOR BOTH DVs!
¨ The meaning of the result in normal-people terms
Lab 5 Discussion
¨ 3 main components ¤ Review findings of our experiment–consistent with
hypothesis? n How results compare to Bransford and Johnson (1972)? n How did our study differ? WHY NOTABLE DIFFERENCES? n What might explain these findings?
¤ Limitations of our study, future directions ¤ Implications of these studies Remember to use APA style citations throughout
Lab 5 References
¨ Include ¤ Complete citation for Bransford and Johnson (1972)
n Can be found through Google Scholar or PsycInfo