Final answer:
The statement regarding cohorts is false, as cohorts are groups of subjects with shared characteristics, not necessarily varying demographics. A positive correlation indicates a relationship where variables change together but does not inherently imply health benefits.
Step-by-step explanation:
The statement "A cohort is a group of subjects of different ages, weights, genders, and health statuses" is false. A cohort typically refers to a group of subjects who share a defining characteristic, often being studied to observe changes over time or differences within the group. Cohorts are usually chosen to be similar in important characteristics to ensure that the variables being studied are less likely to be influenced by other factors.
Focusing on the correlation between variables, a true statement would be "A positive correlation means there are health benefits to the variable under investigation" only if the research specifically demonstrates that increased levels of one variable are associated with improvements in health outcomes. However, the term 'positive correlation' simply means that two variables move in the same direction, not necessarily that there are health benefits.