Week 4
No description yet. This curated deck is ready for daily study.
Card preview (24)
What is an experiment?
an experiment there is manipulation of one variable, usually while keeping everything else constant
What do experiments provide evidence for?
Experiments provide some evidence of cause and effect
What is an observational study?
Illuminate patterns (correlation or associations between variables), but are unable to fully disentangle the effects of measured explanatory variables and unmeasured confounding variables
What is a confounding variable?
a variable that masks or distort the causal relationship between measured variables in a study
What is the limitation of observational studies?
An observational study might not be able to pull apart confounding variables because they will co-occur
Is correlation symmetrical?
yes both variables will be correlated with each other
Is Causation symmetrical?
no – Smoking causes heart attacks, but heart attacks do not cause smoking
What is the goal when designing a experiment?
to eliminate bias and reduce sample error.
What is bias?
a systematic discrepancy between the estimate you would obtain, IF you could sample a population again and again, and the true population characteristic
What is sampling error?
The difference between an estimate and the population parameter being estimated caused by chance
What does reducing sampling error achieve?
increases precision
What do control groups do?
Eliminates bias
What does Randomization do?
Eliminates bias
What does Blinding do?
Eliminates bias
what does Replication do?
Reduces sample error
what does Balance do?
Reduces sample error
what does Blocking do?
Reduces sample error
what do Sub-replicates achieve?
Reduces sample error
Paired designs purpose?
Reduces sample error
• Consistency of conditions purpose?
Reduces sample error
What is a control group?
A simultaneous control group is a set of subjects that are treated in the same way as the treatment group in all ways except that the treatment is not applied
What will happen with randomization?
Randomization will roughly equalize confounding factors The confounding factors will still exist, but the effect will not be skewed
What does Pseudo-randomization do?
almost always generates bias
definition of blinding
Blinding is when either (or both) an experimenter and subject are unaware of treatment and control