RESS - Ebook

Question 1

What type of data do bar charts use?

Answer 1

Categorical (ordinal and nominal) and Numerical discrete

Question 2

What type of data do pie charts use?

Answer 2

Categorical (ordinal and nominal)

Question 3

What type of data do histograms use?

Answer 3

Numerical Continuous

Question 4

In a histogram what does the area of the bar and the height of the bar mean?

Answer 4

Area: Frequency
Height: Frequency/Class width

Question 5

What is standard deviation?

Answer 5

Average distance of all the points from the MEAN!

Larger the SD- bigger distribution of data

Question 6

With what type of data is SD used

Answer 6

Normally distributed

Question 7

What is IQR?

Answer 7

Q1 - Median - Q3

Between Q1 and Q3 is the IQR which is where 50% of the distribution lies

Question 8

With what type of data is IQR used?

Answer 8

Skewed data

Question 9

Define Incidence

Answer 9

Incidence is the number of new cases over a specific time period
Number of new cases/ Number at risk

Question 10

Define Prevalence

Answer 10

Prevalence is the number of cases of disease at a particular time point
Number of people with a disease/ number of people in a population

Question 11

Define Mortality

Answer 11

Mortality is the number of people dying from a disease

Number of people who die from a disease/Number of people who die in general

Question 12

Define Case Fatality

Answer 12

number dying in period from disease / number with the disease in period

Question 13

What is risk?

Answer 13

Synonymous with probability

Number of new cases/ Number at risk

Question 14

What is a risk ratio?

Answer 14

Shows relative risk in an exposed and unexposed group

Question 15

When is risk ratio used?

Answer 15

Cohort studies to show relative risk!

Question 16

What is odds?

Answer 16

Number of time an event occurs / Number of time it doesn’t occur

Question 17

What is odds ratio?

Answer 17

Shows relative risk

Question 18

When is odds ratio used?

Answer 18

Case control studies and RCT to show relative risk!

Question 19

What two things can determine relative risk?

Answer 19

Odds ratio (RCT and case control) and Risk ratio (cohort studies)

Question 20

What does a RR of 1 show?

Answer 20

means risk in exposed = risk in unexposed so no benefit or harm

Question 21

What does RR <1 show?

Answer 21

means risk in exposed < risk in unexposed exposure is protective

Question 22

What does RR >1 show?

Answer 22

means risk in exposed > risk in unexposed exposure is harmful

Question 23

What does Gaussian distribution show?

Answer 23

Normal distribution in the shape of a bell curve

Question 24

What are features of normal distribution?

Answer 24

Values symmetric around the mean
Greatest frequency is at the mean
Normal distribution is symmetric around the mean median and mode

Question 25

What are features of a normal distribution curve?

Answer 25

SD is how broad the bell is Area under the curve is 1 Mean = 0 SD= 1

Question 26

How do you make probability statements about a variable using a distribution curve?

Answer 26

Transform the distribution curve to a standard normal distribution curve

Question 27

What is standard error?

Answer 27

Used to calculate confidence intervals of the mean (Standard deviation needs to be known to calculate standard error) (Is a measure of the precision of the sample mean) The larger the sample size the lower the standard error

Question 28

What is a confidence interval

Answer 28

A range of feasible values that the true (mean) value is believed to be within (usually 95% probability)

Question 29

What does it mean if a confidence interval crosses 0?

Answer 29

If a confidence interval crosses this is not statistically significant as the effect of the variable could be 0

Question 30

How is the SE and thus confidence interval calculated if you have known SD?

Answer 30

Known SD if >200 samples | Confidence interval calculated using critical values from standard normal distribution

Question 31

How is the SE and thus confidence interval calculated if you have estimated SD?

Answer 31

Estimated if sample size <200 | Confidence interval calculated using students t distribution

Question 32

What has a wider range 90% CI or 95%

Answer 32

95% (as to be 95% sure the ranges will be wider)

Question 33

What is a null hypothesis?

Answer 33

Opposite to hypothesis; assumes nothing happens

Question 34

What is an alternative hypothesis?

Answer 34

Has two possible outcomes e.g. drug will decrease hypertension or increase hypertension

Question 35

What assumptions are necessary for the test statistic?

Answer 35

1 - The variable; change in bp has to be normally distributed 2- The samples are independence i.e. from different patients

Question 36

What is the p value?

Answer 36

The probability that the null hypothesis is true | Lower the P value the less likely the null hypothesis is true

Question 37

When is the p value statistically significant?

Answer 37

When it is <0.005

Question 38

Are confidence intervals adequate for hypothesis testing?

Answer 38

Yes

Question 39

What is parsons correlation coefficient?

Answer 39

r | Measure of linear correlation between two numerical values

Question 40

R values =0, >0, <0, 1 and - 1

Answer 40

``` =0 Linear relationship >0 Positive correlation <0 Negative correlation 1 perfect correlation -1 perfect negative correlation ```

Question 41

What value of correlation is treated with suspicion

Answer 41

<0.7

Question 42

When should pearsons coefficient not be used?

Answer 42

No linear relationship Outliers Subgroups i.e. not numeric One or both variables are not normally distributed

Question 43

When pearsons coefficient can't be used what is used instead?

Answer 43

Speerman rank correlation

Question 44

When is superman rank correlation used?

Answer 44

Ordinal data Small sample size Data not normally distributed

Question 45

In linear regression analysis what is on the X and Y axis

Answer 45

X axis: independent variable | Y axis: Dependent variable

Question 46

What requirements are needed for regression analysis?

Answer 46

Linear relationship | Normally distributed

Question 47

What is the chi squared test?

Answer 47

Association between two categorical variables

Question 48

What does the chi squared test compare?

Answer 48

Contingency tables from; results observed and results expected if null hypothesis was true

Question 49

What conditions are required fro chi squared test?

Answer 49

4 cells should be more than 1 | Three of these should be more than 5

Question 50

If conditions are not met for a chi squared test what else can be used?

Answer 50

Fishers exact test

Question 51

Sensitivity

Answer 51

How well a test detects a condition

Question 52

Specificity

Answer 52

How well a test correctly excludes those without the condition

Question 53

Positive predictive value

Answer 53

Probability someone has the condition if they test positive

Question 54

Negative predictive value

Answer 54

Probability someone doesn’t have the condition if they test negative

Question 55

Failure Event

Answer 55

The time a person leaves a study is known

Question 56

Censory

Answer 56

Leaving a study before the event occurs or enters late

Question 57

Left Censory

Answer 57

Disease present before the entered (not sure what happened before they entered)

Question 58

Right censory

Answer 58

People in the study did not reach a failure before the end (i.e for HIV drug an individual left country or died from non HIV related cause)

Question 59

Survival Function

Answer 59

Chance of survival until a certain time

Question 60

Hazard Function

Answer 60

Chance of an instantaneous failure

Question 61

Kapplan meir plot

Answer 61

Shows survival as a series of steps | It steps down every time a failure is observed