Biostatistics

Question 1

How is sensitivity calculated?

Answer 1

TP/(TP+FN)

Question 2

How is specificity calculated?

Answer 2

TN/(TN+FP)

Question 3

What is a factorial design study?

Answer 3

Involves 2 or more experimental interventions, each with 2 or more variables that are studied independently (e.g. different BP meds with pts divided into different BP goals)

Question 4

How is the positive predictive value affected by prevalence?

Answer 4

Increased PPV with increased disease prevalence?

Question 5

How is negative predictive value affected by prevalence?

Answer 5

Increased NNV with decreased disease prevelance

Question 6

What is attributable risk percent (ARP) calculated? - represents the excess risk in a population that can be explained by exposure to a particular risk factor

Answer 6

ARP = (risk in exposed - risk in unexposed)/ (risk in exposed)
aka ARP=(RR - 1)/RR

Question 7

What is the “rare disease assumption”?

Answer 7

If a disease is rare, the odds ratio from a case-control study approximates the RR (cohort).

Question 8

How is RR calculated?

Answer 8

RR=[a/(a+b)]/[c/(c+d)]

Question 9

How is OR calculated?

Answer 9

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