Flashcards in EBM Deck (30):

1

## What p value would cause one to accept the null hypothesis of a chi-squared analysis?

### p > 0.05

2

## When would linear regression be used?

###
To help predict a variable from another variable

(So you draw out a line chart and use one value to predict the other)

3

## When would an un-paired t-test be used?

### To compare the means of two unrelated populations

4

## When would a paired t-test be used?

### To compare the means of two related populations (e.g. the same population before and after)

5

## What is a meta-analysis?

### Combining results from different studies

6

## What is sensitivity?

###
Measures the proportion of +ve's identified (e.g % of sick people identified as sick).

TRUE POSITIVE RATE

7

## What is specificity?

###
Measure the proportion of -ve's identified (e.g. % of healthy people correctly identified as not sick).

TRUE NEGATIVE RATE

8

## The most important 3 factors when assessing a clinical trial are...

### Validity, results and clinical relevance

9

## When would you use regression and what are the two types?

###
To predict dependant variable from independant

Can correct for confunding variables

Linear- when continous outcomes

Logistic- When binary outcomes

10

## What is the t-test used for?

###
Tests the change in mean between two groups

CONTINUOUS VARIABLE

11

## What is the chi-squared test used for?

###
Version of t-test to see if expected freq = anticipated frequency (testing null hypothesis)

BINARY VARIABLES ONLY

12

## What equation is used to calculate odds ?

###
Number of individuals with outcome

----------------------------------------------------

Number of individuals without outcome

13

## What equation is used to calculate odds ratio?

###
odds of the outcome in one group (e.g. treatment)

---------------------------------------------------------------------------

odds of the outcome in another group (e.g. control)

14

## What is implied by an odds ratio of 1?

### No difference between the two groups

15

## What is used to test the significance of odds ratio's?

###
Chi squared

Allows us to compare proportions across two different groups.

Tells us whether the comparison is statistically significant (it gives a p value).

16

## What is Multiple (or multivariate) logistic regression used for?

### Used to assess the predictive value of one or more variables on a YES/NO outcome

17

## You are asked: "How does smoking affect the likelihood of having pancreatitis, after accounting for (or ‘unconfounded by’ or ‘independent of’) alcohol consumption, BMI, etc.?”. What do you use to find the answer?

### Multiple logistic regression

18

## What is positive predictive value?

###
Probability that the disease is present when the test is positive.

19

## What is negative predictive value?

###
Probability that the disease is not present when the test is negative.

20

## What equation is used to work out positive predictive value?

###
True positives

-----------------------------------

(true positives + false positives)

21

## What equation is used to work out negative predictive value?

###
True negatives

------------------------------------------

(true negatives + false negatives)

22

## The true positive rate is also known as.....?

### Sensitivity

23

## False positive rate is also known as....

### (1- Specificity)

24

## What is found on the x and y axis of ROC curves?

###
x axis = (1- specificity)

y axis= Sensitivity

25

## What does ROC stand for?

### Receiver Operating Characteristic

26

## What are ROC curves used for in a clinical context?

### Setting test cut off points

27

## What does the null hypothesis usually state?

###
That the difference between the two means is 0

(so intervention makes no difference)

28

## What p value would cause you to reject the null hypothesis?

### p less than 0.05

29

## What is a categorical variable?

### Can take a fixed number of values

30