Basic Epidemiology (28 mins)
Scroll down to Chapter 6 titled "Epidemiology and prevention: Chronic noncommunicable Diseases" and read the section titled "Screening" (pages 110-114). Answer 'Study questions' 6.3 and 6.4 on page 114.
Click http://apps.who.int/iris/bitstream/handle/10665/43541/9241547073_eng.pdf link to open resource.