Behavioral Science

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Behavioral Science
2011-07-13 07:12:45
Behavioral USMLE

Behavioral Science / Epidemiology for the USMLE 1
Show Answers:

  1. What is the formula for sensitivity?
    Sensitivity = TP/(TP + FN)
  2. What is the formula for specificity?
    Specificity = TN/(TN + FP)
  3. What is Positive Predictive Value?
    • what proportion of positive results are true
    • PPV = TP/(TP + FP)
  4. What is Negative Predictive Value?
    • what proportion of those with a negative test do no have the disease
    • NPV = TN/(TN + FN)
  5. What is Accuracy?
    • the total percentage that is correctly selected - whether positve or negative
    • Accuracy = (TP + TN) / total screened patients
  6. What is reliability?
    ability of a test to measure something consistently
  7. What type of bias is present when you have used only hospital records to estimate population prevalence?
    Berkson Bias
  8. What type of bias occurs when information is gathered in a manner that distorts the information?
    Hawthorne Effect
  9. What statistic do we use in cross-sectional studies?
  10. What is Relative Risk?
    • it compares the incidence in the exposed group to the unexposed
    • RR = exposed with disease / un-exposed with disease
  11. What is Attributable Risk?
    • deals with absolute numbers;
    • how many more cases in the exposed group than the unexposed?
    • AR = exposed with disease - unexposed with disease
  12. What is the Number Needed to Treat?
  13. What the heck is an Odds Ratio?
    • used in case-control studies, estimates the strength of a risk factor
    • if someone has the disease, what are the odds that they had the risk factor?
    • OR = product of trues / product of falses