That's Random
While random sampling makes a sample similar to the population, this ensures samples are randomly similar to each other.
What is random assignment?
This is fundamental to making random assignment work
What is equating on expectation?
The only internal validity threat that randomization prevents from occurring
What is selection bias?
If groups in a study mature at different rates and their posttest scores reflect differences between the two groups, this may possibly be a reason.
What is differential maturation?
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A key issue in this design is
What is the nature of the control condition?
Random assignment is different from other design features based on this one special characteristic
What is it can yield unbiased estimates of the average treatment effect.
Random assignment equates groups on..
What is the expected value of all variables at pretest (measured or not)?
In a random assignment, the only systematic difference between groups is
What is treatment?
Not so fast. Even with random assignment and pretest, this threat to internal validity is still possible
What is a testing?
Randomization ensures that confounding variables are unlikely to be ____ with the treatment condition a unit receives.
What is correlated?
Pretests are useful because they allow better diagnosis of and adjustment for these 3 things…
What is attrition, facilitate use of statistical techniques that increase statistical power, and see whether treatment is equally effective at different levels of the pretest?
Given equal groups at pretest, the control group posttest serves as this.
What is a source of counterfactual inference for the treatment group posttest
A randomized experiment distributes threats randomly over conditions, making it implausible for this about cause and effect relationships to happen.
What are alternative explanations?