Part 2: Types of Studies

Question 1

What are the 4 different studies?

Answer 1

1. RCT
2. Cohort
3. Cross-sectional
4. Ecological

Question 2

What is a longitudinal study?

Answer 2

A study which goes through a period of time (over a long period of time)

Question 3

What is the opposite of longitudinal study?

Answer 3

Cross sectional study (one point in time)

Question 4

Which occurrence type can longitudinal studies be associated with?

Answer 4

Incidence

Question 5

Which occurrence type can cross sectional be associated with?

Answer 5

Prevalence

Question 6

Which studies out of the 4 are longitudinal?

Answer 6

RCT
Cohort
Could be Ecological

Question 7

Which studies out of the 4 are cross sectional?

Answer 7

Cross-sectional

Could be Ecological

Question 8

What is the usual study objective of RCT?

Answer 8

Investigate the effects of different interventions (exposures) on dis-ease incidence in different group of individuals

Question 9

What is the usual study objective of Cohort studies?

Answer 9

Investigate associations (effects) between risk factors (exposures) and dis-ease incidence in different groups of individuals.

Question 10

What is the usual study objective of Cross-sectional studies?

Answer 10

To measure dis-ease prevalence in defined groups of individuals.

Investigate associations between exposures and dis-ease prevalence in the groups.

Question 11

What is the usual study objective of Ecological study?

Answer 11

Investigate associations between exposures and dis-ease prevalence or incidence in different groups of populations.

Question 12

Which studies have individuals?

Answer 12

RCT
Cohort
Cross-sectional

Question 13

Which study sees groups of populations rather than individuals?

Answer 13

Ecological

Question 14

What is the most useful application of the RCT?

Answer 14

Effect of interventions like in:

• New therapies
• Drugss

Question 15

What is the most useful application of the Cohort?

Answer 15

Studying the causes of dis-ease incidence or the effects of interventions

Question 16

What is the most useful application of the Cross-sectional?

Answer 16

Measuring the prevalence/burden of dis-ease in different groups and populations

Question 17

What is the most useful application of the Ecological?

Answer 17

Studying trends and causes of dis-ease incidence and prevalence

Question 18

Which studies are experimental?

Answer 18

RCT

Could be Ecological

Question 19

What is the opposite of experimental?

Answer 19

Observational

Question 20

Which studies are observational?

Answer 20

Cohort
Cross-sectional
Could be Ecological

Question 21

What does observational mean?

Answer 21

That the study undertakers are only viewing the participants, not forcing them to use anything (ethical)

Question 22

What does experimental mean?

Answer 22

We do not know the outcome (like a new drug) so it could be bad or good but we are essentially experimenting on people in the RCT trials

Question 23

How is RCT allocated?

Answer 23

Random

Question 24

How is Cohort study allocated?

Answer 24

Measurement

Question 25

How is Cross sectional allocated?

Answer 25

Measurement (usually by questionnaire or survey)

Question 26

How is Ecological allocated?

Answer 26

Could be random or measurement

Question 27

What does random allocation give rise to?

Answer 27

No confounding, allocation non random error

Question 28

What does measurement error give rise to?

Answer 28

Confounding (allocation non random error)

Question 29

Which studies have confounding?

Answer 29

Cohort
Cross-sectional
Ecological

Question 30

What is the weakness of longitudinal studies?

Answer 30

Long time give rise to

• maintenance error
• also $$$$$$$$$$$

Question 31

What gives rise to cross sectional (quick) studies?

Answer 31

Quick,

• no maintenance issue
• cheap as $

Question 32

What is the main strength of RCT? (1)

Answer 32

Limited confounding

Question 33

What is the main strength of Cohort studies? (2)

Answer 33

Usually cheaper than RCT (even though longitudinal)

E measured before O so NO recall bias

Question 34

What is the main strength of Cross-sectional studies? (3)

Answer 34

Cheap

Quick, no follow up so NO MAINTENENCE

Best design for assessing prevalence/burden of dis-ease in population

Question 35

What is the main strength of Ecological? (3)

Answer 35

Cheap

Quick

Efficient for rare outcomes

Question 36

If a study is generally quick (no follow up) what does this have a positive for?

Answer 36

No maintenance non random error

Question 37

What are the main weaknesses of RCT?

Answer 37

Ethical limitations

$$$$$$$$ so normally small participants so more random error and could be statistically insignificant

Maintenance error common

Question 38

Which studies have follow ups?

Answer 38

RCT
Cohort
Could be ecological if it is a collection of RCT’s

Question 39

What can follow up’s lead to (the weakness)

Answer 39

Maintenance non random error

Question 40

What are the main weaknesses of Cohort?

Answer 40

Confounding (due to measurement allocation)

Maintenance error (long term studies because exposure is not controlled by the invesitgators)

Question 41

What is the main weakness of Cross-sectional studies?

Answer 41

Uncertain time sequence so reverse causality

If period prevalence, can be subject to recall bias

Confounding (allocation is by measurement; survey)

Question 42

What is the main weakness of Ecological studies?

Answer 42

Confounding very common