Flashcards in Probability and Statistical Significance Deck (40):

1

## What are the two way studies can have errors?

###
Caused by chance (Random Error)

Not Causes by chance (Bias or Systematic error)

2

## Random Error

###
Due to Chance

Does not bias a study

3

## Systematic error

###
Due to Bias

Error that is inherent to the study method being used and results in a predictable and repeatable error for each observation

4

## 'Statistically significant'

### if a study result is unlikely to have occurred by chance

5

## A Chance occurrence

### Something that happens unpredictably without discernible human intention or with no observable cause: Caused by chance or random variation

6

## Random Variation

### there is an error in every measurement. If we measure something over and over again, we will get slightly different measurements each time and a few measurements may be extreme

7

## Statistical inference

### if we measure something only once, how sure are we that our measurement has been caused by chance

8

## What are the two methods used for estimating how much random variation there is in a study and whether the result was likely to have been caused by chance?

###
Confidence Intervals

P-values

9

## Confidence Intervals

###
Estimates how much random variation there is in our measurement

The range of values where the true value of our measurement can be found (assuming the study wasn't biased)

For some measures it can estimate whether the measure was likely to have been caused by chance

10

## P-values

### Used to estimate whether the measure was likely to have been caused by chance or not

11

## If the 95% Confidence Interval odds ratio DOES NOT INCLUDE ONE....

### the odds ratio is statistically significant

12

## When the odds ration is equal to 1

### there is no association

13

## Odds Ratio is greater than one and confidence interval doesn't include one

###
Positive association

Statistically significant

14

## Odds Ratio is greater than one, but confidence interval includes one

###
No association

Not statistically significant

15

## Odds Ratio is less than one and confidence interval doesn't include one

###
Negative association

Statistically significant

16

## Odds Ratio is less than one and confidence interval includes one

###
No association

Not statistically significant

17

## What value must the P-value be less than to be statistically significant?

### 0.05

18

## Null Hypothesis

### The 'hypothesis of no association' - this is no association between exposure and disease

19

## Alternative hypothesis

### The 'research question' - that there is an association between exposure and disease

20

## If the p-value is less than 0.05

### Reject the null hypothesis and accept the alternative hypothesis

21

## If the p-value is greater than 0.05

### Accept the null hypothesis and reject the alternative hypothesis

22

## Type I (alpha) error: False Positive

###
Rejecting the null when it is NOT false

p=0.05

23

## Type II (Beta) error: False Negative

###
Not rejecting the null when it is false (an association truthfully exists)

Conventionally set at 0.20

24

## Categorical

### The variable is broken into discrete categories

25

## Nominal

### Named (not ordered)

26

## Ordinal

### Named and ordered but no constant value between ranks

27

## Continuous

### The variable is numeric and can have any one of many possible values

28

## Mean

###
Average

Sum of all values/ # of data points

VERY sensitive to extreme values

29

## Median

###
The value which is the center, with half of the data points "below" and half of the data points "above"

30

## Mode

### The most frequently occurring value/observation

31

## Dispersion

###
Describes how closely the values are gathered around the center of distribution

32

## What are the two measures of dispersion?

###
Range

Standard Deviation

33

## Range

### the difference between the minimum and maximum

34

## Standard Deviation

### The average distance between each measurement and the mean

35

## What are the two statistical tests?

###
Chi-squared test

Student's T-Test

36

## Chi-squared test

###
difference in proportions

Used for categorical data

All two by two tables

37

## Student's T-test

###
difference in means

Compares the average of two groups

used for continuous data

38

## Correlation

### Measures the strength ad direction of a linear relationship between two continuous variables

39

## Is an r value greater than 0.80 strong or weak correlation?

### Strong

40