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