Statistics

Question 1

How does RANZCOG classify their levels of evidence?

Answer 1

From level 1-5

Question 2

List the levels of evidence and what they mean in RANZCOG?

Answer 2

I - systematic review of RCTs
II - High quality RCT
III - Observational case control or cohort studies
IV - case report or case series (non analytical)
V - expert opinion

Question 3

Give 3 examples of descriptive study types?

Answer 3

Correlational
Cross sectional
Case reports and case series

Question 4

Give two examples of analytical observational studies

Answer 4

case controlled studies

cohort studies

Question 5

give two examples of analytical interventional study types

Answer 5

Randomised controlled trials

clinical controlled trials

Question 6

Give an example of a secondary study

Answer 6

Systematic review

Question 7

Describe case control studies

Answer 7

Cases are selected on basis of outcome
carefully matched to control group who do not experience the outcome
examine exposure retrospectively

Question 8

Describe cohort studies

Answer 8

Experimental group selected on basis of exposure
carefully matched to control group who are not exposed
Examine outcome status prospectively

Question 9

In what scenario are case control studies good? list another benefit

Answer 9

Good for rare outcomes and common exposures

Relatively fast and cheap

Question 10

In what scenario are cohort studies good? list another benefit

Answer 10

good for rare exposures and common outcomes

most rigorous of epidemiological studies

Question 11

Describe a case report

Answer 11

a case is a detailed report on the profile of a single patient
rare events are usually reported in case reports

Question 12

Describe what a case series is

Answer 12

Case series is a report on a series of patients with an outcome of interest

Question 13

Give 3 disadvantages of descriptive studies

Answer 13

highly susceptible to bias
suggests association not causation
does not establish temporal relationship between cause and effect
may confuse characteristics of a group with characteristics of an individual

Question 14

List 3 types of bias that affect case control studies

Answer 14

recall bias
selection bias
measurement error

Question 15

describe detection bias and list a way it can be mitigated

Answer 15

where measurements are taken differently between treatment groups
mitigated by blinding

Question 16

describe selection bias and a method to mitigate this form of bias

Answer 16

where subject allocation results in treatment groups that are systematically different, apart from in the intervention being studied.
Can be mitigated by randomisation

Question 17

Describe observer bias and how to mitigate this

Answer 17

where the data collector is able to be subjective about the outcome
blinding, hard outcomes (measurable)

Question 18

describe publication bias and how this can be mitigated

Answer 18

when negative studies are less likely to be published than positive ones
clinical trial registries

Question 19

describe recall bias and how this can be mitigated

Answer 19

altered reporting of symptoms by patients depending on which group they have been allocated to
blinding

Question 20

describe response bias and how to mitigate

Answer 20

when patients who enrolled for a trial are not representative of a population making the results not generalisable
Random sampling

Question 21

Describe the Hawthorne effect

Answer 21

When the process of doing the study improves the outcome

use of control group + masking the study intent from patients/participants and observers