the investigation of cause and effect

Question 1

What three types of studies come under observational study?

Answer 1

Cross-sectional studies

Case-control studies

Cohort studies

Question 2

what is a cross sectional study?

Answer 2

try to determine the cause and effect when measuring exposure and disease at one point in time to for a hypothesis

Question 3

What is a case control study?

Answer 3

investigate the cause and effect by comparing exposure in

• cases (with disease or outcome)
• controls (without disease or outcome)

usually retrieve

hypothesis generating or testing

Question 4

What is a cohort study?

Answer 4

Cohort followed over a period of time

Investigate cause and effect by comparing outcome in :

• Exposed people
• Non - exposed people

usually prospective
- Looking forward in time over a log period

Hypothesis generating or testing

Question 5

What is an experimental study?

Answer 5

2 types
- randomised controlled clinical trials
- non-randomised controlled clinical trials

researchers introduce an intervention and study effects

usually randomised, subject grouped by chance

Question 6

explain randomised controlled clinical trials

Answer 6

gold standard
- ability to minimise bias obtained in information obtained from participants

random assignment of participants to experimental treatment or a control group (placebo)

patients kept unaware of which treatment received in trial, Known as blind study or single blinded

Question 7

When would a non-randomised controlled clinical trial be used instead of a randomised one?

Answer 7

only used when random allocation is problematic

More prone to bias

Question 8

explain a crossover design of a randomised controlled clinical trial

Answer 8

All participants enter both groups, in random order, often separated by a washout period in which they receive no treatment

Cancels many forms of bias as patients are exposed to all protocols

Question 9

What is cause and effect?

Answer 9

a cause is anything that produces an effect or result

The knowledge of cause and effect relationship can lead to successful prevention strategies

Question 10

What 3 steps can causation be summarised as?

Answer 10

1. investigation of statistical association
2. investigation of temporal relationships
3. Elimination of alternative explanations

Question 11

Explain the investigation of statistical association in terms of cause and effect

Answer 11

must first find an association between the risk and the disease

statistical association can be:
1. strength
2. consistency
3. specific
4. plausible
5. Dos-response relationship

Question 12

Explain investigation of temporal relationships in terms of cause and effect

Answer 12

causal relationship depends on the temporal relationship

to show causation the suspected causal factor must have occurred before the effect or disease developing

Question 13

Explain the elimination of alternative explanations in terms of cause and effect

Answer 13

need to show there is no other reason for the effect other than the causal factor

Question 14

What is internal validity?

Answer 14

How well the study answers the clinical question for
the sample.

Measure and measurements.

Question 15

What is External validity?

Answer 15

How well the study answer the clinical question for
the population.

Internal validity and accurate sampling

Question 16

What are the sources of bias within study design?

Answer 16

Measurement bias

Recall bias

selection bias

systematic bias

Question 17

explain measurement bias ang how it can be controlled

Answer 17

can occur during collection of baseline or follow up data

can be differential or non differential

can compromise internal or external validity

can be controlled by using the same instruments for all measurements and double blinding the study

Question 18

What is a differential in terms of study bias?

Answer 18

miss classification

occurs when a measurement device leads to incomparable measurements between groups

Question 19

What is recall bias?

Answer 19

can take many forms, may occur if people who have experienced an adverse event such as a disease, they are more likely to recall previous risk factors than those who have never experienced the event

compromises internal and external validity

Question 20

What is selection bias and how is it controlled?

Answer 20

happens when participant chosen for the study influences the outcome of the study

also happens when participants are allowed to select the group they want to join

this can be controlled using randomisation sampling methods from the target population

Question 21

name 4 more types of systematic bias

Answer 21

Performance bias

exclusion bias

detection bias

publication bias

Question 22

What is performance bias?

Answer 22

refers to systematic differences in the care provided or in exposure to factors other than intervention of interest

Question 23

What is exclusion bias?

Answer 23

Systematic differences in withdrawals from the trial

common reasons for exclusion of patients : ineligibility, protocol violation, early outcome, loss to follow up after study

Question 24

What is detection bias?

Answer 24

Systematic differences in outcome assessment

cause an over or under estimate of the cause of the effect

Neyman bias (preferential detection of mild, slowly progressive cases of disease)

Question 25

What is publication bias?

Answer 25

Selective publication of positive results

reluctance to publish papers with negative results

distortion of literature

Question 26

What is random error and how does it influence the study design?

Answer 26

Random error refers to distortion of data in any direction.

Produces finding that are too high and too low in
approximately equal amounts.

Decreases the probability of finding a real association by
reducing the statistical power of a study.

less damaging than bias

Question 27

What is cofounding effect and how does it effect the study design?

Answer 27

Confounding is the confusion between two factors that lead to an
outcome.

Can lead to a false identification or obscuration of a cause-and-effect
relationship.

Compromises internal and external validity.

Question 28

What is Effect modification and how does it effect study design?

Answer 28

in effect modification the directoion or strength of an association between two variables differ according to the value of a third variable

known as interaction

occurs when a cause and effect relationship is modified by using another variable

compromises internal and external validity

can be controlled using statistical modelling

Question 29

What is a qualitative study

Answer 29

Seeks a deeper truth, form of social enquiry where the
researcher seeks to understand human behaviour.

Based on:
 Action
 Observation, Interview
 Classification
 Inductive
 Theoretical
 Validity

Question 30

What are the ttributes of a qualitative study?

Answer 30

People focused

use of textual data

exploration in natural settings

inductive reasoning

systematic and flexible

small sample size

rich descriptions

identifies patterns

builds theories

Question 31

What is a questionnaire based study?

Answer 31

Objective means of collecting information about people’s
knowledge.

can be qualitative or quantitative depending on questions asked

Based on:
 Questions
 Multiple options
 Simple options (true/false, yes/no)

Question 32

What are the requirements for a questionnaire based study?

Answer 32

Appropriate questions

valid and reliable

appropriate for target pop

clear instruction

questionnaire adequately piloted

appropriate sampling

maximise response rate

data analysis

Question 33

What is secondary literature analysis?

Answer 33

Includes meta-analysis and decision analysis.

Meta-analysis:
 Exposure and outcome examined from the literature.
 Useful when previous studies have sample size.

Decision Analysis:
 Improve clinical decisions.
 Decision trees.

Question 34

What are the steps for a meta analysis?

Answer 34

1. The research question
2. inclusion and exclusion criteria
3. objective method for article selection
4. blind article review and decide on eligibility
5. effect across studies is calculated
6. homogeneity across study is calculated
7. weighting method applied
8. average combined methods is calculated

Question 35

What are the steps to decision analysis?

Answer 35

1. improve clinical decisions
2. decision tree
   2.1 Decision nodes
   2.2 chance node
   2.3 probability values
   2.4 utility values

2.3.1 adopting a given management strat
2.3.2 any possible outcome