Lecture 4 - Understanding Study Designs

Question 1

What is a randomised controlled trial?

Answer 1

When a group of people are randomly separated into 2 groups where the intervention is present and one isn’t (like a treatment group and a control group)

And an outcome is observed

Question 2

What are the advanatages of randomised control trials?

Answer 2

Can state causation
Removes selection bias
Helps limit effects of confounding factors

Can compare current treatment to new treatments

Question 3

What are the disadvantages of randomised control trails?

Answer 3

Time consuming
Expensive (need large sample sizes)
Ethical issues

Question 4

What is a confounding factor?

Answer 4

A factor that has influenced the results of the study without being accounted for

Question 5

What is a cohort study?

Answer 5

Observational study where data is collected at certain points over a period of time from a group of participants BASED ON EXPOSURE TO A RISK FACTOR

Question 6

What is a prospective cohort study?

Answer 6

Where a cohort of participants are selected based on being exposed to a risk factor (or not) then they are followed up (did they develop the disease?)

Question 7

What is a retrospective cohort study?

Answer 7

A cohort of participants recruited from the past and data is then collected from their records

(Do these patients who smoke 20 a day now have lung cancer?)

Question 8

What are the advantages of a cohort study?

Answer 8

Good for studying range of outcomes
Good for rare exposures
Can establish exposure preceded outcome

Question 9

What are the disadvantages of a cohort study?

Answer 9

Time consuming
Expensive
Not good for rare OUTCOMEs

Question 10

What is a case-control study?

Answer 10

Type of observational study where a population is selected and date is collected retrospectively

So picks a patient with a disease then looks back to see if they had the exposure

Question 11

What is the difference between a case-control study and a cohort study?

Answer 11

Case-control = starts with the case (disease) looks back for the cause

Cohort = starts with cause, looks forward or back for the causes

Question 12

What are the advantages for case-control studies?

Answer 12

Can investigate multiple exposures for a single outcome
Good for rare diseases
No loss to follow up

Question 13

What are the disadvantages for case-control studies?

Answer 13

Not good for rare exposures
Can only study one outcome
Potential for reverse causality (disease may have lead to the exposure)

Question 14

What is meant by statistical power?

Answer 14

The sample is large enough to determine whether there is a difference between the 2 groups

How likely the study is tot distinguish an actual effect from one off chance

Question 15

What helps increase statistical power?

Answer 15

Having a large sample size

Question 16

What is bias?

Answer 16

Any deviation from the truth in data collection, analysis, interpretation which can lead to false conclusions

Question 17

What is selection bias?

Answer 17

When the sample used in the study is not representative to the whole population

Question 18

What is information bias?

Answer 18

bias refers to errors or inaccuracies in data collection, measurement, or reporting within a study.

Question 19

What is observer bias?

Answer 19

occurs when the expectations or beliefs of the person conducting an experiment influence the results.

Question 20

What is recall bias?

Answer 20

When theres a systematic difference between the accuracy and the completeness of particapnts memories and recollections