Final answer:
In epidemiology, validity is measured primarily through incidence, tracking new cases of a disease, and prevalence, looking at all cases within a population. Different types of validity, like ecological, construct, and face validity, ensure that studies accurately represent what they aim to measure.
Step-by-step explanation:
In epidemiology, the two ways in which we measure validity are through incidence and prevalence. Incidence is the measure of new cases of a disease during a specific time frame, used to identify and assess risk factors. Prevalence, in contrast, includes both new and existing cases and helps indicate the overall health of a population. Both these measures are critical for determining disease burden and guiding public health policies.
Validity itself is crucial to understand if a study or measure accurately assesses what it's intended to. It encompasses different types, including ecological validity, which looks at the generalizability of results to real-world settings; construct validity, ensuring a variable represents what it's supposed to; and face validity, a superficial assessment of whether a test seems to measure what it claims to measure.