You test a population to see how prevalent covid-19 is, how it's spreading, whether your containment efforts are working, what variants are spreading. You test

You test a population to see how prevalent covid-19 is, how it's spreading, whether your containment efforts are working, what variants are spreading. You test an individual to help you decide on appropriate healthcare. It's really important that people who test negative still behave as if they might have covid and might spread covid.