Study design

Question 1

What is a cohort study?

Answer 1

Longitudinal forward prospective study
Cross sectional at points- follow up

Question 2

State 3 strengths and 3 weaknesses of cohort study?

Answer 2

Strengths
1) Demonstrate causal effects
2) Multiple diseases studied
3) Multiple exposure studied

Disadvantages
1) Expensive and time consuming
2) Not suitable rare diseases
3) Need deal confounding factors

Question 3

What is cross sectional study?

Answer 3

Investigate what happening at certain point in time
Outcome and exposures measured simultaneously

Question 4

State 3 strengths and weaknesses of cross sectional?

Answer 4

Strength
1) Relatively fast and inexpensive
2) Rapid feedback current events
3) Multiple outcome and exposure studied

Disadvantage
1) Not suitable rare disease
2) Limited to study causation
3) Can effected selection bias and confounding factors

Question 5

If investigators assign exposure to patients what trial?

Answer 5

Rct
Depend random allocation

Question 6

What are two types study design?

Answer 6

Experimental
Observational

Question 7

Explain case control study?

Answer 7

Retrospective
Past exposures
Sample taken based disease

Question 8

State 4 advantages and 4 disadvantages of case control ?

Answer 8

Strength
1) Quick and inexpensive
2) Suitable rare diseases
3) Multiple exposures studied
4) Suitable transient exposures (outbreaks)

Weaknesses
1) Only single disease studied
2) Exposure data needed before start study
3) Can affected selection bias and confounding factors

Question 9

Explain RCT?

Answer 9

Have entry criteria-randomly split groups
Double blind

Question 10

What is gold standard?

Answer 10

RCT

Question 11

State 4 weaknesses of RCT?

Answer 11

1) Expensive
2) Not practical show long term
3) Affected by non compliance
4) Might not ethical

Question 12

Give 3 examples of confounding factors?

Answer 12

Income
Sex
Age

Question 13

Define association
Define causation

Answer 13

Association- statistical link between exposure and disease- may not reflect cause and effect relationship

Causation- statistical link where disease directly caused by exposure

Question 14

What are 2 types of sampling?

Answer 14

Probability (random) methods
Non-probability (non random) methods

Question 15

State 2 disadvantages for non probability (non random) methods?

Answer 15

Sampling error can’t measured
High potential bia

Convenient

Question 16

State advantage for probability (random) methods?

Answer 16

Sampling error can be measured

Question 17

Explain simple random sampling?
Disadvantages?

Answer 17

Each member of pop has equal prob being selected
Eg lottery

Disadvantages
Not always good rep- minority groups
Not as precise stratified sampling

Question 18

Explain systematic random sampling?
Disadvantages?

Answer 18

Members of population selected at equal intervals
K=N/n
Disadvantages
Need complete list pop
Large standard error
Periodicity pattern- characteristics occur regular intervals in pop

Easy to do

Question 19

Explain stratified random sampling?

Answer 19

Pop split into groups- samples taken each group
Eg 3 ppl from each of 20 group

Question 20

State advantages and disadvantages of stratified random sampling?

Answer 20

Advantages
Increase representation
Can prod population estimates
Smaller standard error

Disadvantages
Require prior info
Expensive

Question 21

Explain cluster sampling?

Answer 21

Population participated clusters- sample clusters selected
Clusters made to be similar

Question 22

List advantages and disadvantages of cluster sampling?

Answer 22

Advantages
Don’t need complete list population
Cheap

Disadvantages
High standard error- decrease statistical precision