This is a great place to start. When using ground beef to make hamburger patties, be sure to select the right meat. Lean ground beef like ground sirloin or the 7% fat meat will tend to make dry burgers.
Changes in lifestyles, nutrition, and ethnic composition of populations lead to changes in the distribution of body dimensions (e.g. the obesity epidemic), and require regular updating of anthropometric data collections.
If only wealthy people have phones, then being wealthy is correlated with ever being polled in the first place. Thus the opinions of wealthy people will be overrepresented. An observation selection effect exists when some property of a thing is correlated with the observer existing in the first place. The study of such effects is sometimes called anthropic reasoning or anthropics, after the anthropic principle.