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Flashcards in Stats equations to memorise Deck (16):
1

How do you calculate NNT?

1/ARR
(ARR = CER-EER)

2

How to calculate sensitivity?

Sensitivity = TP/(TP+FN)

3

How to calculate specificity?

Specificity = TN/(TN+FP)

4

How to calculate positive predictive value?

PPV = TP/(TP+FP)

5

How to calculate negative predictive value?

NPP = TN/(TN+FN)

6

How to calculate likelihood ratio for a positive result?

Likelihood +ive = sensitivity/(1-specificity)

7

How to calculate likelihood ratio for a negative result?

Liklihood -ive = (1-sensitivty)/specificity)

8

How to calculate odds ratio?

a) Odds of outcome in cases = number with/number without
b) Odds of outcome in controls = number with/number without
c) Odds ratio = a/b

9

What study design usually gives its answer as odds ratio?

Case-control

10

How do you calculate relative risk reduction?

Absolute risk change/control event rate

I.e., RRR = ARR/CER

= (ERR-CER)/CER

11

How to calculate risk of an outcome in a group?

Number of people developing the condition as a proportion of the total.
Eg, 1000 people exposed to a risk factor. 200 of them die. Risk = 200/1000 = 0.2

12

How do you calculate standard error?

SE = standard deviation/square root of n.

13

False negative rate = ?

False negative rate = 1-sensitivity

14

Calculate experimental event ratio or control event ratio? What is it expressed as?

Number who had the outcome/total number treated.
Expressed as a decimal or as a %

15

How to calculate relative risk?

EER/CER

16

How to calculate absolute risk?

EER-CER