To offer a concrete example here, survery respondents are often biased based on who actually sees and fills out a survey. A common technique used to overcome th

To offer a concrete example here, survery respondents are often biased based on who actually sees and fills out a survey. A common technique used to overcome this non-representative sample is called post-stratification. There are, of course, limits to post stratification especially in instances of low sample sizes, but techniques to overcome issues with data are well known.