Final answer:
Studies in question are classified based on whether there's manipulation of variables or observational measurement. An experimental study involves controlled manipulation, while observational studies like cohort, case-control, and cross-sectional involve monitoring without intervention.
Step-by-step explanation:
The question involves classifying different types of studies into various categories such as Experimental, OBSERVATIONAL COHORT, Observational case-control, Observational cross-sectional, or other non-analytical or epidemiological studies. To clarify, an experimental study involves manipulation of variables in a controlled environment to observe the effects, while observational studies simply monitor and measure characteristics without influencing the subjects or variables.
A cohort study is an observational study where a group is followed over a period to see the effect of certain factors on the development of outcomes, whereas a case-control study compares subjects with a trait to those without retrospectively. Cross-sectional studies capture data at a single point in time, providing a 'snapshot' of a particular condition or characteristic.
Based on the provided examples, study (i) where 400 men are divided into two groups to take aspirin or placebo is classified as A. Experimental, because it involves the random assignment of treatments. Study (ii), where a group of similar subjects is followed over time, refers to a B. Observational cohort study. Studies (iii) and (iv) were not specified but can be classified based on whether the study has a retrospective nature looking for past behaviors (C. Observational case-control) or if it's measuring current characteristics at one time (D. Observational cross-sectional).