Data Collection & Observational Studies

Views:
 
Category: Education
     
 

Presentation Description

How to sample in experimental and observational studies

Comments

Presentation Transcript

Data Collection Principles:

Data Collection Principles By Farrokh Alemi, Ph.D.

Sampling:

Examine a subset of cases Sampling

Randomization:

Examine a subset of cases Randomization

Non-response Bias:

Angry patients do not take satisfaction surveys Non-response Bias

Convenience Bias:

Convenience Bias

Confounding Variable:

Confounding Variable Real Cause Presumed Cause Effect

Confounding Variable:

Confounding Variable Fire Firemen on scene Burning house

Blaming Heroes:

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

Think it Through:

Think it Through 10% 60% 0.06% 0.04% 0.54% 0.46% 60% 40% 40% 90%

Think it Through:

Think it Through 10% 60% 0.06% 0.04% 0.54% 0.46% 60% 40% 40% 90%

Oops:

Oops

Observational Studies:

Observational Studies

Retrospective Studies:

Cases Exposed Controls not Exposed Outcomes Outcomes Future Past Present Time Investigator Retrospective Studies

Retrospective Studies:

Retrospective Studies Cases Exposed Controls not Exposed Outcomes Outcomes Future Past Present Time Investigator

Implied Equivalence:

Implied Equivalence Future Past Investigator Cases Exposed Controls not Exposed Outcomes Outcomes Present Time Matched Otherwise

Vioxx Study:

Vioxx Study

Take Home Lesson:

In observational studies, controls are matched to cases in all relevant variables except for exposure to treatment Take Home Lesson

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 Do One: Patient ID Treated Age Outcome Random 1 Yes Young Positive 0.24 2 No Young Positive 0.85 3 Yes Old Negative 0.64 4 No Old Negative 0.70 5 No Old Negative 0.87 6 No Old Negative 0.72 7 No Old Negative 0.86 8 No Young Negative 0.16 9 No Young Positive 0.17

authorStream Live Help