research methodology

Question 1

advantages of a cross sectional study

Answer 1

cheap and easy

can measure multiple variables at the same time

Question 2

disadvantages of a cross sectional study

Answer 2

cannot measure temporality
cannot measure incidence
information bias( recall and selection)

Question 3

what happens in a cross sectional study

Answer 3

exposure and outcome are measured at one point in time

Question 4

what happens in a cohort study

Answer 4

prospective:
outcome has not occurred yet
participants selected on basis of exposure
follow up to see if outcome occurs

retrospective:
study begins when outcome has already occurred
participants selected on basis of exposure (not outcome status)

Question 5

advantages of a cohort study

Answer 5

temporality
can calculate incidence
useful for rare exposures
study multiples outcomes of exposure

Question 6

disadvantages of a cohort study

Answer 6

loss to follow-up
detection bias
time consuming and expensive

Question 7

what happens in a case control

Answer 7

identify cases (those with the outcome), choose controls(must be the same as cases but without outcome) and measure exposure in both cases and controls

Question 8

advantages of a case control

Answer 8

efficient
relatively quick
good for rare outcomes
can study multiple exposures

Question 9

disadvantages of a case control

Answer 9

selection bias (selection of controls)
information bias( recall)
can only calculate odds ratio (not risk)
no temporality

Question 10

what happens in ecological studies

Answer 10

studies with population or group level variables

Question 11

advantages of ecological studies

Answer 11

hypothesis generation

quick and cheap

Question 12

disadvantages of ecological studies

Answer 12

ecological fallacy(association at population level no longer true at individual level)
confounding bias
cannot determine causality

Question 13

what happens in a RCT

Answer 13

exposure assigned randomly

Question 14

advantages of RCT

Answer 14

Minimal confounding/bias

strong evidence

Question 15

disadvantages

Answer 15

ethical issues
time- consuming, expensive
loss to follow up

Question 16

what is blinding

Answer 16

hiding who got what from participants, clinicians, statisticians ( double blinding where both the participant and the researchers etc. are blinded

Question 17

what is the aim of blinding

Answer 17

to reduce bias

Question 18

what are the measures of disease occurrence

Answer 18

prevalence
incidence
(these tell us how much disease there is)

Question 19

what are the measures of disease association

Answer 19

relative measures 
prevalence ratio
incidence( risk ratio)
odd ratio
( compares the occurrence of disease in different exposure groups)