Experimental Research (designs and threats to internal validity) Flashcards
why are researchers interested in causality?
- to understand how (social) reality works
- the intervene in that reality
what are the conditions causality?
- covariance: there should be a relationship between cause and outcome
- temporal precedence: the cause should precede the outcome in time
- internal validity: alternative explanations for the relationship should be ruled out
what is the best way to meet all conditions of causality?
randomized experiment
what is a randomized experiment?
-groups can be assumed to be similar by randomization
-one variable is manipulated (varied) by the researcher
-the researcher measures the effect of this manipulation on another variable (the outcome)
what are the threats to internal validity?
design confounds and selection effect
what are design confounds?
a second variable that happens to vary systematically along with the intended independent variable
what is the selection effect?
the groups are not comparable at the start of the experiment
how do you avoid selection effects?
forming the groups using random assignment
what is the goal of random assignment?
to make sure that the mean and variance in scores, on all variables, measured and unmeasured, are similar for both groups at the onset of the study
randomization issues
sometimes nonethical or infeasible, sometimes possible but contamination occurs
what is contamination in randomization
when participants in the experimental group communicate with participants in the control group, participants do not adhere to the treatment, or there is influence from researchers
what should an experimental research question include?
PICO: population, intervention, comparison, and outcome
what is the population in PICO?
the group of people the researcher wishes to investigate
what is the intervention in PICO?
the experimental condition
what is the comparison in PICO
the control group
what is the outcome in PICO?
the dependent variable
