What is the difference between representative samples and random samples, and how are they are used to reduce sampling bias?

A simple random sample is used to represent the entire data population. A stratified random sample divides the population into smaller groups based on shared characteristics.

Why bother conducting experiments on treatments for COVID-19 (e.g., chloroquine) instead of relying on anecdotal evidence about their effectiveness? Random assignment is discussed.

Previously, I described different sampling methods and explained why random sampling is an important component of researching treatments for COVID-19.