data collection principles
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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DATA COLLECTION PRINCIPLES
By Farrokh Alemi, Ph.D.
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Examine a subset of cases
Sampling
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Examine a subset of cases
Randomization
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Angry patients do not take satisfaction surveys
Non-response Bias
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Convenience Bias
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Confounding VariableReal Cause
Presumed Cause
Effect
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Confounding VariableFire
Firemen on scene
Burning house
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Blaming HeroesSeverity of Illness
Medication Treatment
Patient Outcomes
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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
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Think it Through
All patient
s
Report on web
Satisfied
Not satisfie
d
Do not report
Satisfied
Not satisfie
d
10%
60% 0.06%
0.04%
0.54%
0.46%
60%
40%
40%90%
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Think it Through10
%
60%
40%
90%
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Oops
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Observational Studies
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Cases Exposed
Controls not
Exposed
Outcomes
Outcomes
FuturePastPresentTime
Investigator
Retrospective Studies
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Retrospective Studies
Cases Exposed
Controls not
Exposed
Outcomes
Outcomes
FuturePastPresentTime
Investigator
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Implied Equivalence
FuturePast
InvestigatorCases
Exposed
Controls not
Exposed
Outcomes
Outcomes
PresentTime
Mat
ched
O
ther
wis
e
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Vioxx Study
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In observational studies, controls are matched to cases in all relevant variables except for exposure to treatment
Take Home Lesson
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Identify cases. Select two controls that match on age & have lowest random number. Calculate the proportion of success for case and matched controls
Do One:
Patient ID Treated Age Outcome Random 1 Yes Young Positive 0.242 No Young Positive 0.853 Yes Old Negative 0.644 No Old Negative 0.705 No Old Negative 0.876 No Old Negative 0.727 No Old Negative 0.868 No Young Negative 0.169 No Young Positive 0.17