Probability and Statistical Significance

Question 1

What are the two way studies can have errors?

Answer 1

Caused by chance (Random Error)

Not Causes by chance (Bias or Systematic error)

Question 2

Random Error

Answer 2

Due to Chance

Does not bias a study

Question 3

Systematic error

Answer 3

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

Question 4

‘Statistically significant’

Answer 4

if a study result is unlikely to have occurred by chance

Question 5

A Chance occurrence

Answer 5

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

Question 6

Random Variation

Answer 6

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

Question 7

Statistical inference

Answer 7

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

Question 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?

Answer 8

Confidence Intervals

P-values

Question 9

Confidence Intervals

Answer 9

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

Question 10

P-values

Answer 10

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

Question 11

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

Answer 11

the odds ratio is statistically significant

Question 12

When the odds ration is equal to 1

Answer 12

there is no association

Question 13

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

Answer 13

Positive association

Statistically significant

Question 14

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

Answer 14

No association

Not statistically significant

Question 15

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

Answer 15

Negative association

Statistically significant

Question 16

Odds Ratio is less than one and confidence interval includes one

Answer 16

No association

Not statistically significant

Question 17

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

Answer 17

0.05

Question 18

Null Hypothesis

Answer 18

The ‘hypothesis of no association’ - this is no association between exposure and disease

Question 19

Alternative hypothesis

Answer 19

The ‘research question’ - that there is an association between exposure and disease

Question 20

If the p-value is less than 0.05

Answer 20

Reject the null hypothesis and accept the alternative hypothesis

Question 21

If the p-value is greater than 0.05

Answer 21

Accept the null hypothesis and reject the alternative hypothesis

Question 22

Type I (alpha) error: False Positive

Answer 22

Rejecting the null when it is NOT false

p=0.05

Question 23

Type II (Beta) error: False Negative

Answer 23

Not rejecting the null when it is false (an association truthfully exists)
Conventionally set at 0.20

Question 24

Categorical

Answer 24

The variable is broken into discrete categories

Question 25

Nominal

Answer 25

Named (not ordered)

Question 26

Ordinal

Answer 26

Named and ordered but no constant value between ranks

Question 27

Continuous

Answer 27

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

Question 28

Mean

Answer 28

Average
Sum of all values/ # of data points
VERY sensitive to extreme values

Question 29

Median

Answer 29

The value which is the center, with half of the data points “below” and half of the data points “above”

Question 30

Mode

Answer 30

The most frequently occurring value/observation

Question 31

Dispersion

Answer 31

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

Question 32

What are the two measures of dispersion?

Answer 32

Range

Standard Deviation

Question 33

Range

Answer 33

the difference between the minimum and maximum

Question 34

Standard Deviation

Answer 34

The average distance between each measurement and the mean

Question 35

What are the two statistical tests?

Answer 35

Chi-squared test

Student’s T-Test

Question 36

Chi-squared test

Answer 36

difference in proportions
Used for categorical data
All two by two tables

Question 37

Student’s T-test

Answer 37

difference in means
Compares the average of two groups
used for continuous data

Question 38

Correlation

Answer 38

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

Question 39

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

Answer 39

Strong

Question 40

Is an r value less than 0.80 strong or weak correlation?

Answer 40

Weak