Microsoft Word research method fm doc

II. Analytic studies 
Analytic studies may be defined as studies used to test hypotheses concerning the 
relationship between a suspected risk factor and an outcome and to measure the 
magnitude
of the association and its statistical significance. 
Analytic study designs can be divided into two broad design strategies: Observational and 
intervention. 
Observational studies 
ƒ
No human intervention involved in assigning study groups; simply observe the 
relationship between exposure and disease. 
ƒ
Subject to many potential biases, but by careful design and analysis, many of these 
biases can be minimized.
ƒ
Examples of observational studies: comparative cross-sectional, cohort and case-
control studies. 
a) Comparative cross-sectional studies
:
Depending on the purpose of a given 
study, a cross-sectional survey could have an analytical component (see section 6.3, 2c, 
above). 
b) Cohort studies:
Study groups identified by exposure status prior to ascertainment 
of their disease status and both exposed and unexposed groups followed in identical manner 
until they develop the disease under study, they die, the study ends, or they are lost to follow-
up. 

---

Research methodology 
30
Strengths and limitations of the cohort study design
 
Strengths: 
ƒ
Is of particular value when the exposure is rare 
ƒ
Can 
examine 
multiple effects
of a single exposure 
ƒ
Allows 
direct 
measurement of incidence of disease in the exposed and non-exposed 
groups. 
 
Limitations: 
ƒ
Is inefficient for the evaluation of rare diseases 
ƒ
Expensive and time consuming 
ƒ
Validity of the results can be seriously affected by losses to follow-up.