200 likes | 293 Views
Data Collection Principles. By Farrokh Alemi, Ph.D. Sampling. Examine a subset of cases . Randomization. Examine a subset of cases . Non-response Bias. Angry patients do not take satisfaction surveys. Convenience Bias. Confounding Variable. Real Cause. Presumed Cause. Effect.
E N D
Data Collection Principles By Farrokh Alemi, Ph.D.
Sampling Examine a subset of cases
Randomization Examine a subset of cases
Non-response Bias Angry patients do not take satisfaction surveys
Confounding Variable Real Cause Presumed Cause Effect
Confounding Variable Fire Firemen on scene Burning house
Blaming Heroes Severity of Illness Medication Treatment Patient Outcomes
Think it Through Supposed 10% of patients report their attitudes on the web and 40% of patients who write a comment on web are negative, what percent of our patients are dissatisfied?
Think it Through 0.06% 60% 40% 10% 0.04% 90% 0.54% 60% 40% 0.46%
Think it Through 40% 10% 90% 60%
Retrospective Studies Investigator Cases Exposed Outcomes Outcomes Controls not Exposed Past Future Time Present
Retrospective Studies Investigator Cases Exposed Outcomes Outcomes Controls not Exposed Past Future Time Present
Implied Equivalence Investigator Cases Exposed Outcomes Matched Otherwise Outcomes Controls not Exposed Past Future Time Present
Take Home Lesson In observational studies, controls are matched to cases in all relevant variables except for exposure to treatment
Do One: Identify cases. Select two controls that match on age & have lowest random number. Calculate the proportion of success for case and matched controls