Flashcards in Stats Deck (34):

1

## formula for NNT

###
NNT = 1/ARR

ARR = absolute risk reduction

2

## type I error

###
rejecting the null hypothesis when it's actually correct

false positive study

alpha

3

## type II error

###
failure to reject the null hypothesis appropriately

false negative study

beta

4

## failure to reject the null hypothesis appropriately

### type II error

5

## rejecting the null hypothesis when it's actually correct

### type I error

6

## What 3 factors do you need to look at to determine the appropriate type of statistical test to perform?

###
1. is the distribution parametric or not?

2. is your data continuous, nominal/ordinal, or categorical?

3. are your tested populations dependent or independent?

7

## Sensitivity =

### TP / TP+FN

8

## Specificity =

### TN / TN+FP

9

## Power

###
1 - beta

beta = type II error rate

10

## PPV =

### TP / TP+FP

11

## NPV =

### TN / TN+FN

12

## Incidence vs Prevalence

###
Incidence = RATE of new diseases over a period of time

Prevalence = number of existing disease cases at a specific POINT in time

13

## What do you need to calculate the sample size for a study?

###
1. the effect size

2. the type I error rate

3. the type II error rate

14

## what is the reciprocal of the rate difference?

### the NNT

15

## What is the other name for the Mann-Whitney U test?

### Wilcoxon rank-sum test

16

## What is another name for the Wilcoxon rank-sum test?

### Mann-Whitney U test

17

## What is the t-test?

### statistical test for parametric, continuous data that is independent

18

## what is the paired t-test?

### statistical test for parametric, continuous data that is paired

19

## what is the ANOVA?

### statistical test for parametric, continuous data with 3 or more independent groups

20

## what is the wilcoxon signed-rank sum test?

###
statistical test for non-parametric, continuous data that is paired

non-parametric corollary to paired t-test

21

## what is the wilcoxon ranked-sum test?

###
statistical test for non-parametric, continuous data that is independent

nonparametric corollary to t-test

also called the mann-whitney u test

22

## what is the kruskal-wallis?

###
statistical test for non-parametric, continuous data with 3 or more independent groups

nonparametric corollary to ANOVA

23

## what is the Chi-square test?

### statistical test for parametric, categorical data with independent groups

24

## what is the Fisher's exact test?

### statistical test for parametric, categorical data with independent groups if there are <5 measurements/group

25

## what is logistic regression?

### statistical test to predict the relationship between a DICHOTOMOUS outcome vs a set of variables while controlling for other variables in the analysis

26

## what is Bonferroni's correction

### a method to correct for multiple repeated testing on the same data set

27

## what is Kolmogorov-Smirnov?

### test to determine if data is parametric or not

28

## what is Shaprio-Wilk?

### test to determine if the data is parametric or not

29

## LR +

###
= (positive test/presence of disease) / (positive test/absence of disease)

= sensitivity / (1 - specificity)

30

## LR -

###
= (negative test/presence of disease) / (negative test/absence of disease)

= (1 - sensitivity) / specificity

31

## How do you use LRs?

###
You have to convert the pretest probability to odds

This is pretest probability / (1 - pretest probability)

Then you multiply by the LR

Finally, you convert the odds BACK to the probability!

32

## What are clinically significant LRs?

###
LR + > 10

LR - < 0.1

33

## formula for odds ratio

###
(AxD)/(BxC) in standard 2x2 table

34