Evidence Based Medicine

Question 1

What is meant by a randomised study?

Answer 1

The population receiving the intervention and the population being compared are only difference because of random variation

Question 2

What is meant by a controlled study?

Answer 2

The intervention is being compared to something else: a placebo, a gold-standard, best practice

Question 3

What is meant by a trial?

Answer 3

An experimental intervention, with a beginning and an endpoint

Question 4

How is an odds ratio calculated?

Answer 4

Quantifies the strength of the association between two events

Odds even when exposed/ odds event when not exposed

Question 5

State the two ways of describing probability

Answer 5

P value

Confidence interval

Question 6

Define P value

Answer 6

A numerical value indicating the probability that this observation has occurred due to chance

Question 7

Define confidence interval

Answer 7

A way of indicating a range of values which probably contain the ‘true’ value
e.g. there is a 5% chance of the true value lying outside of these limits

Question 8

The null hypothesis states that…

Answer 8

There is no relationship between the study variables

Question 9

There is a clear difference between confidence intervals in the two groups. Why could this be?

Answer 9

The null hypothesis is false
Random chance
Confounding (creates false effect)

Question 10

There is no clear difference between confidence intervals in the two groups. Why could this be?

Answer 10

The null hypothesis is true
Random chance
Confounding (hides the effect)
The effect size is too small

Question 11

What is publication bias?

Answer 11

When papers that are published on a topic are an incomplete subset of all the studies that have been conducted

Question 12

List ways in which publication bias is prevented

Answer 12

Data Protection Act (rules for management of personal information)
Caldicott Guardian Approval (access to patient’s records without consent)
Non-clinical ethics committee (non-NHS)
Clinical research ethics committee (doing things to patients)

Question 13

What is meant by internal validity?

Answer 13

How good the research methods used by researchers answer the clinical question
Does the study measure what it sets out to measure?

Question 14

What is meant by external validity?

Answer 14

Will we get the same results in real life settings

Can the results of the study be generalised to a wider population?

Question 15

What is purposive sampling?

Answer 15

Sample units chosen as they have particular features or characteristics

Question 16

What is convenience sampling?

Answer 16

Selection made on basis of who is available

Question 17

What is snowball sampling?

Answer 17

Individuals identifying others to participate

Question 18

What is opportunistic sampling?

Answer 18

Whoever is there

Question 19

Define triangulation in terms of research studies

Answer 19

Area under investigation looked at from different perspectives using 2 or more research methods

Question 20

What is absolute risk?

Answer 20

The number of events in treated or control groups, divided by the number of people in that group

Question 21

What is ARC?

Answer 21

the AR of events in the control group

Question 22

What is ART?

Answer 22

the AR of events in the treatment group

Question 23

What is ARR (absolute risk reduction)?

Answer 23

Probability or chance of an event
Risk in exposed group - risk in non-exposed group
ARC-ART

Question 24

What is RR (relative risk)?

Answer 24

ART/ARC

Question 25

What is RRR (relative risk reduction)?

Answer 25

Ratio of the probability of an outcome in an exposed group to the probability of an outcome in an unexposed group Incidence in exposed/ incidence in not exposed (ARC-ART)/ARC

Question 26

What is NNT (number needed to treat)?

Answer 26

1/ARR

Question 27

Define statistical significance

Answer 27

Likelihood that a relationship between two or more variables is caused by something other than chance

Question 28

Define cohort study

Answer 28

A longitudinal study that samples a cohort (a group of people who share a defining characteristic, typically those who experienced a common event in a selected period, such as birth or graduation), performing a cross-section at INTERVALS THROUGH TIME

Question 29

State two ways of making a confidence interval narrower

Answer 29

Lower variability | Larger sample size

Question 30

What is it called when there is no longer any need to sample more people to reach new conclusions or to back up or challenge existing conclusions?

Answer 30

Saturation

Question 31

What is qualitative research?

Answer 31

Seeks to analyze data which researchers collect from people in relation to their experiences and circumstances

Question 32

What is quantitative research?

Answer 32

Describe and measure the level of occurrences within data on the basis of numbers and calculations

Question 33

What is the difference between a single blind and double blind study?

Answer 33

Single blind = Subjects of the study are left unaware of aspects of the study Double = both subjects and researchers are unaware of 1 or more aspects being sought

Question 34

What is a case-control study?

Answer 34

A type of observational study in which two existing groups differing in outcome are identified and compared on the basis of some supposed causal attribute

Question 35

What is a cross-sectional study?

Answer 35

A type of observational study that analyzes data from a population, or a representative subset, at a specific point in time

Question 36

Define standardised incidence ratio

Answer 36

Ratio of the observed number of cases to the expected number of cases

Question 37

Extremely high satisfaction rates suggests...

Answer 37

Inclusion bias