Rod Jackson

Question 1

What is epidemiology?

Answer 1

The study of frequency (or occurrence) of dis-ease in populations

Question 2

What does the term “dis-ease” mean?

Answer 2

Any health-related event or state - such as death and diabetes

Question 3

What is an occurence?

Answer 3

The transition from a non-diseased state to a dis-eased state

Question 4

What is a population?

Answer 4

Any group of people who share a common factor

Question 5

What type of data is dealt with in epidemiological studies?

Answer 5

Quantitative

Question 6

What are the types of quantitative data?

Answer 6

Categorical and numerical

Question 7

What is categorical data?

Answer 7

Data grouped into categories e.g. man/woman

Question 8

What is numerical data?

Answer 8

Data that takes on numerical values e.g weight and height

Question 9

What are the visual components of the GATE frame?

Answer 9

Triangle Circle Square Arrow

Question 10

What is the GATE frame?

Answer 10

Graph approach to epidemiology

Question 11

What does the triangle represent in the GATE frame?

Answer 11

The participant population

It is divided into 3 parts:
Top = setting
Middle = eligible population
Bottom = Number of study population

Question 12

What does the circle represent in the GATE frame?

Answer 12

Study specific sub-denominators = exposure group and comparison group

Question 13

What does the square represent in the GATE frame?

Answer 13

The numerators (disease outcomes)

Question 14

What does the arrow represent in the GATE frame?

Answer 14

Time

Question 15

How do you deal with numerical data in the GATE frame?

Answer 15

They can either be converted to categorical data or average values can be calculated as dis-ease occurrence

Question 16

What are the two measures of dis-ease occurrence?

Answer 16

Incidence and prevalence

Question 17

What is incidence?

Answer 17

The measure of onsets of dis-ease occurring during a period of time from the population

Question 18

What is represented by the vertical arrow?

Answer 18

Incidence - occurrence measured over a specified period of time

Question 19

What is the equation to calculate incidence

Answer 19

Incidence = (Number of people in group who have dis-ease outcomes/Number of people in population)/Time taken for study

Incidence = (N/D)/T

Unit is outcomes per number of people per time taken for study

Question 20

What is prevalence?

Answer 20

The measure of the number of people with the dis-ease at a point in time from the population

Question 21

When is prevalence used?

Answer 21

When the dis-ease is not easily observable e.g. onset of diabetes cannot be easily measured

Also when the outcome can occur many times in a specified period of time e.g. asthma attacks

Question 22

What does the horizontal arrow represnt?

Answer 22

Prevalence - the occurrence was measured at a point in time

Question 23

What is the equation to calculate prevalence?

Answer 23

Prevalence = Number of people who have the dis-ease /Number of people in population at a point in time

Prevalence = N/D

Unit is the outcomes per people in the study at a specified point in time

Question 24

What is the purpose of epidemiological studies?

Answer 24

To investigate and compare the EGO and CGO and in doing so estimate the association between the outcome and the exposure

Question 25

What is relative risk RR?

Answer 25

EGO / CGO no units

Question 26

What does a RR value of 1 indicate?

Answer 26

EGO = CGO

Question 27

What is risk difference RD?

Answer 27

EGO - CGO units same as occurrence measure

Question 28

What is PECOT?

Answer 28

``` Participants or study population Exposure group Comparison group Outcome Time ``` Memory aid for the 5 parts of epidemiological studies

Question 29

What are the two types of errors?

Answer 29

Random and non-random

Question 30

What are random errors?

Answer 30

Errors caused due to chance

Question 31

What are non-random (systematic) errors?

Answer 31

Errors caused by problems with how the study was designed or conducted

Question 32

What is RAMBOMAN?

Answer 32

Acronym used to identify where non-random errors can occur ``` Recruitment Allocation Maintenance Blind or Objective Measurements Analysis ```

Question 33

How do systematic errors occur in the recruitment process?

Answer 33

1. When a study on a population is done to approximate and apply the results to a wider population the study population must be recruited from the correct setting to represent the wider population - even in the correct process of sampling random error can occur 2. The participants who meet the eligibility criteria from this setting must all be similar enough to fit into the same population 3. The response rate (proportion of people in the eligible population who choose to take part in the study population) must be high enough so that there is no difference between those who accept to take part in the study and reject to take part in the study

Question 34

How do systematic errors occur in the allocation process?

Answer 34

1. Measurement error - EGO and CGO measured incorrectly meaning some participants will be allocated to the wrong group 2. Confounding - when there are differences in the EG and CG other than the exposure that affect the study outcome (existence of confounders)

Question 35

What is a randomised controlled trial?

Answer 35

Study in which the EG and CG are allocated randomly In theory the two groups formed would be very similar minimising confounding

Question 36

What is baseline comparison?

Answer 36

Checking the EG and CG differences before a study is commenced

Question 37

What is concealment of allocation?

Answer 37

A solution to confounding in RCTs where the randomising process can be tampered with. Involves prevention of any possible tampering through study design

Question 38

How can confounding be reduced?

Answer 38

RCTs Larger sample size Stratified analysis (analysis based on differences between groups e.g. age-standardisation)

Question 39

How do systematic errors occur in the maintenance process?

Answer 39

In the ideal study - maintain exposure status - not be exposed to other factors affecting outcome - not drop out of study Any comprised factors introduce maintenance error.

Question 40

How do systematic errors occur in the Blind and Objective measurement process?

Answer 40

Any problem in study design when measuring outcomes will lead to systematic error

Question 41

How is measurement error reduced?

Answer 41

Set outcome to be objective in that they can be measured easily and clearly Blind the participants or investigators or both to the knowledge of the exposure

Question 42

What is random sampling error and why does it occur?

Answer 42

Errors (deviations from the truth) that occur due to chance. Random sampling errors occur because when investigating the effects of an exposure on dis-ease occurrence, everyone in the population cannot be included - hence, a sample is chosen to represent this population and this creates random sampling error.

Question 43

How is random error reduced?

Answer 43

Increase sample size | Do repeats on measurements related to allocation and outcome

Question 44

What does a 95% confidence interval represent?

Answer 44

There is a 95% chance the true value of the occurrence from the whole population is included in the range provided.

Question 45

What does it mean if the confidence interval for EGO and CGO do not overlap?

Answer 45

Reasonable to assume that the difference is significant and true assuming no systematic error was present

Question 46

What does it mean if the confidence interval for a calculated RR value includes 1?

Answer 46

The difference in the EGO and CGO is statistically insignificant

Question 47

What does it mean if the CI for a calculated RD value includes 0?

Answer 47

Difference is not statistically significant

Question 48

What is meta-analyses?

Answer 48

The combination of multiple studies to demonstrate whether or not the exposure has had a real effect