HaDPop

Question 1

How do you calculate total period fertility rate?

Answer 1

Sum of all age specific fertility rates

Question 2

How is standardised mortality ratio calculated?

Answer 2

Observed deaths/expected x 100

Question 3

How is incidence rate calculated>

Answer 3

Cases / (persons x years)

Question 4

How are error factors calculated?

Answer 4

e^ 2 x (sq root of 1/observed event)

Question 5

How are confidence intervals calculated?

Answer 5

Lower = value/error factor
Upper = value x error factor

Question 6

What are two types of selection bias?

Answer 6

Systematic error in how two groups were collected.
Allocation bias
Healthy worker effect

Question 7

How is odds ratio calculated?

Answer 7

(exposed cases x unexposed controls) / (unexposed cases x exposed controls)

Question 8

What is the null hypothesis when talking about an odds ratio?

Answer 8

1

Question 9

What type of studies use odds ratios?

Answer 9

Case control studies

Question 10

What is meant by the cause effect relationship in epidemiology?

Answer 10

Disease results from interplay between host, environment and agent.
A cause is an exposure or factor that increases the probability of disease.
Exposures don’t have to be necessary or sufficient to be a cause

Question 11

What are the bradford hill criteria?

Answer 11

Strength of association
Specificity of association
Biology plausability
Dose response
Consistency of association
Temporal sequence 
Reversibility
Coherence of theory
Analogy

Question 12

What are 2 assumptions of epidemiology?

Answer 12

Disease doesn’t happen at random

Disease has causal and preventable factors that can be identified through systematic investigation

Question 13

What is a clinical trial?

Answer 13

Any form of planned experiment that involves patients and plans to identify the most appropriate method of treatment for future patients with a given condition

Question 14

What is meant by efficacy?

Answer 14

The ability of a healthcare intervention to improve the health of a particular group under specific conditions

Question 15

What are 3 characteristics of a good clinical trial?

Answer 15

Fair
Reproducible
Controlled (ie uses controls)

Question 16

What are some reasons for differences in otucomes between different patient groups in clinical trials?

Answer 16

Chance
Patient knows type of treatment
Assessor knows type of treatment
Treating clinician knows type of treatment
One treatment is more effective than another

Question 17

Why do pre-defined outcomes need to be set for clinical trials?

Answer 17

To agree criteria for measurement and assessment of outcomes
To prevent repeated analyses
To give protocol for data collection

Question 18

How do we minimise losses to follow up?

Answer 18

Make follow up practical, convenient and simple
Be honest about commitment
Avoid coercion or inducements
Maintain contact with participant

Question 19

What is meant by clinical equipoise?

Answer 19

There’s reasonable uncertainty or genuine ignorance of the better treatment of intervention

Question 20

What is meant be a trial being scientifically robust?

Answer 20

That a trial can be judged scientifically either by looking at what’s actually being researched or by looking at the safety and ethics of the trial

Question 21

What is classed as ethical recruitment?

Answer 21

That there’s no inappropriate inclusion of communities unlikely to benefit from results, participants with higher risk of harm than benefit, participants likely to be excluded from analysis
And no inappropriate exclusion of people who differ from a homogenous group, people who are difficult to gain valid consent from

Question 22

What factors are need for consent to be valid?

Answer 22

Knowledgeable informant
Appropriate information
Informed participant
Competent decision maker
Legitimate authoriser 
Voluntariness

Question 23

What is a systematic review?

Answer 23

Overview of primary studies that used explicit and reproducible methods. Involves a systematic literature search then an appraisal and synthesis. May involve a meta-analysis

Question 24

What is a meta analysis?

Answer 24

Quantitative synthesis of two or more primary studies that addressed the same hypothesis in the same way

Question 25

What is the purpose of a meta analysis?

Answer 25

To facilitate the synthesis of a large number of study results
To systematically collate study results
TO reduce problems of interpretation due to variations in sampling
TO quantify effect sizes and their uncertainty as a pooled estimate

Question 26

How are meta-analyses carried out?

Answer 26

Odds ratios are carried out for each study and these are then combined to give a pooled estimate odds ratio. Studies are then weighted according to their size and uncertainty of result so a higher error factor will get a higher rating. Results are then compiled into a forest plot.

Question 27

Why is heterogeneity a problem with meta-analyses?

Answer 27

Ideally all studies would be identical for analysis but it’s inevitable that some will be different

Question 28

How are forest plots interpreted?

Answer 28

The solid line down the center is the null hypothesis
THe diamond is the overall odds ratio with the edges of the diamond showing the overall confidence intervals.
Boxes are individual odds ratios with size relating to weight given
Lines from boxes show individual confidence intervals
Dotted line shows overall odds ratio in relation to all studies

Question 29

What is the difference between the fixed effect and the random effects models for meta-analysis?

Answer 29

Fixed effects - assumes studies are estimating exactly the same effect so only shows 1 true effect line
Random effects assumes studies are estimating similar effect sizes so there’s mean true effect lines but also trial specific true effect lines which widens confidence intervals and makes weighting more even

Question 30

How is publication bias tested for?

Answer 30

Use statistical test
Check meta-analysis protocol for method of study selection
Create funnel plot with results plotted against their size. Should be balanced