Stats

Question 1

Draw out the 2x2 contingency table and stats used to determine the diagnostic utility of a test or measure

Answer 1

Reference Standard (+)    Ref Stand (-)
DX test (+)                a. TRUE (+)                 b. FALSE (+)
Dx test (-)                 c. FALSE (-)                 d. TRUE (-)

Question 2

Describe and give the formula for overall accuracy

Answer 2

The percentage of individuals who are correctly diagnosed. (a+d)/(a+b+c+d)

Question 3

sensitivity

Answer 3

The proportion of pts WITH a condition who have a (+) test result (a/a+c)

Question 4

specificity

Answer 4

The proportion of pts WITHOUT a condition who have a (-) test result (d/b+d)

Question 5

positive predictive value

Answer 5

the proportion of individuals with a (+) test result who have the condition (a/a+b)

Question 6

negative predictive value

Answer 6

the proportion of individuals with a (-) test result who do not have the condition (d/c+d)

Question 7

pos likelihood ratio

Answer 7

if test is positive..the increase in odds favoring the condition Sens/(1-Spec)

Question 8

neg likelihood ratio

Answer 8

if test is negative…the decrease in odds favoring the condition (1-Sens)/Spec

Question 9

Give the values for large, moderate, small and rarely important changes in +LR

Answer 9

Large: >10
Mod: 5-10
Small: 2-5
Rarely important: 1-2

Question 10

Give values for large, moderate, small and rarely important changes in -LR

Answer 10

Large: <.1
Mod: .1-.2
Small: .2-.5
Rarely important: .5-1.0

Question 11

Give the ICC or k values for sub/mod/fair/slight/no agreememt

Answer 11

substantial: .81-1
moderate: .61-.8
fair: .41-.60
slight: .11-.40
no agreement: .0-1.0