Biostatistics/epidemiology/ethics/IPED things

Question 1

What is the calculation for odds ratio?

Answer 1

OR=(a/b)/(c/d) or a shortcut is OR=(a x d)/(b x c)

Question 2

What is attrition bias?

Answer 2

Loss of patients to follow-up, which happens disproportionately between the exposed and unexposed groups. This is a form of selection bias.

Question 3

How are 95% and 99% confidence intervals calculated?

Answer 3

95%= mean ±1.96 SD/√n and 99%=mean ±2.58 SD/√n

Question 4

What is the equation of attributable risk percent (ARP)?

Answer 4

ARP=100 x [(risk in exposed - risk in unexposed)/risk in exposed]

It is the risk in an exposed population which can be explained by exposure to a particular risk factor.

E.g. there is a 5 x increased risk of esophageal cancer in smokers compared to non-smokers. ARP=100 x (5-1)/5
ARP=100 x 4/5 = 80%

Question 5

What is the best way to avoid wrong-site surgery?

Answer 5

Have two health care workers (e.g. nurse and physician) do an INDEPENDENT verification of patient, procedure and site.

Question 6

What is effect modification?

Answer 6

It is present when the effect of the main exposure on the outcome is modified by the presence of another variable (not a form of bias).

Question 7

What is the Hawthorne effect?

Answer 7

Observer effect: The tendency of study subjects to change their behavior as a result of their awareness that they are being studied.

Question 8

What is the Pygmalion effect?

Answer 8

The fact that a researcher’s beliefs in the efficacy of treatment can potentially affect the outcome.

Question 9

What is the calculation for incidence?

Answer 9

(New cases)/(Population at risk) where population at risk = population - people who currently have the disease.

Question 10

How is accuracy calculated?

Answer 10

(# true positives + # true negatives)/(# observations)