HADPOP

Question 1

What is a forest plot?

Answer 1

An aide to meta-analyses which pools the results of all the studies to give one, overall result

Question 2

Why is a higher weighting given to larger studies in forest plots?

Answer 2

They often have a lower standard deviation, which is the criterion for weighting

Question 3

What is heterogeneity?

Answer 3

Two studies that measure the same thing and have similar results

Question 4

Why would a random effects model be used over a fixed effect model in forest plots?

Answer 4

The heterogeneity is low. Random effects models allow for future hypothetical results

Question 5

What test is used for publication bias?

Answer 5

A line is drawn through the odds ratios of the CONCLUSIVE studies and reflected onto the inconclusive side. A gaping hole indicates publication bias

Question 6

How often are censuses conducted?

Answer 6

Every ten years

Question 7

What data can be drawn from a census?

Answer 7

Unemployment, overcrowding, single parents, basic amenities

Question 8

Give the three measures of fertility

Answer 8

Crude Birth Rate - live births per 1,000
General Fertility Rate - live births per 1,000 fertile females
Total Period Fertility Rate - the number of births every year the average fertile woman would have. Integers indicate a birth

Question 9

What is the replacement level in the western world?

Answer 9

2.07

Question 10

Give the rough equation for prevalence of disease

Answer 10

Incidence x length of disease

Question 11

What is the Standardised Mortality Rate?

Answer 11

The comparison in expected deaths between two populations if the age-sex distributions were identical

Question 12

What is relative risk?

Answer 12

How much more/ less likely am I to suffer a disease compared to him/her?

Question 13

What is absolute risk?

Answer 13

What is my lifetime risk of having a heart attack?

Question 14

Define confounding factors

Answer 14

A factor that is related to both the exposure and the outcome. Can skew results and cannot be gotten rid of

Question 15

What is the p value?

Answer 15

When the null hypothesis is true, the p value is the probability that the observed results would be consistent with this

Question 16

When the p value is below 0.05, what statement do we say about the null?

Answer 16

The observations are significant

Question 17

When the p value is above 0.05, what can we say?

Answer 17

There is insufficient evidence to reject the null

Question 18

Give the equation for error factor

Answer 18

Exp( 2 x (root (1/new cases)))

Question 19

The incidence rate ratio is inferred from what type of study?

Answer 19

Cohort

Question 20

The incidence rate ratio is a type of what broader type of risk?

Answer 20

Relative risk

Question 21

The standardised mortality ratio is susceptible to what type of bias?

Answer 21

Selection. The selected population may not be appropriate for comparison

Question 22

What is survivor bias in the case of a cohort study?

Answer 22

A number of people within one group die so, in the later stages, you are comparing the fitter subset of the group

Question 23

Give the advantages of cohort studies

Answer 23

Establishing temporal sequence
Studying a rare exposure
Studying a range of outcomes

Question 24

Give the disadvantages of cohort studies

Answer 24

Labour intensive/ time consuming
Poor at studying rare outcomes
Susceptible to confounding

Question 25

Why are case control studies used?

Answer 25

To infer causality
For rare diseases
Cheap

Question 26

What biases are common in case-control studies?

Answer 26

Information- people wrongly remember their exposure

Selection - the controls are inappropriately selected

Question 27

What is a nested case-control study?

Answer 27

A cohort study that holds a case-control within it as people start to develop disease and their exposures can be assessed retrospectively

Question 28

What equation gives the odds ratio?

Answer 28

AD/BC
A - exposed cases
B - exposed controls
C - unexposed cases
D - unexposed controls

Question 29

What are Koch’s three postulates of disease?

Answer 29

Necessary - the cause always precedes the disease
Specific - the cause only gives that disease and no other
Sufficient - the cause on its own gives the disease

Question 30

Give the nine Bradford-Hill criteria for disease

Answer 30

Association features
- strength of association
- specificity of association
- consistency of association 
Exposure/ outcome features
- temporal sequence
- dose response
- reversibility
Other evidence
- coherence of theory
- biological plausibility
- analogy

Question 31

RCTs reduce what type of bias?

Answer 31

Allocation - people are intentionally put in one subset based on perceived health and possible results

Question 32

How do RCTs reduce confounding?

Answer 32

The groups are picked randomly so, theoretically, the confounding affects both equally

Question 33

What is the placebo effect?

Answer 33

People get better for taking a pill that has no biological mechanism

Question 34

What bias is the basis for blinding in RCTs?

Answer 34

Measurement - if the assessor knows the treatment allocation, they might change their outcome assessment

Question 35

How do we reduce losses to follow-up?

Answer 35

Maintain contact with participants
Avoid coercion
Be honest about commitment required
Make follow-ups practical for participants

Question 36

What are the two ways that we can assess RCT results?

Answer 36

As treated - those who actually took the drug

Pragmatic/ intention to treat - those who were given the drug (some may not have actually taken it)

Question 37

Give the four bases of trial ethics

Answer 37

Beneficence, non-maleficence, justice and autonomy

Question 38

What aspects are assessed for ethics?

Answer 38

Clinical equipoise
Scientifically robust
Ethical recruitment 
Valid consent
Voluntariness of participants