Such volcanoes are devastating, but very rare. The last one happened at Toba in Sumatra, Indonesia, 74,000 years ago. The active volcanic system at Yellowstone National Park has resulted in super-eruptions-the most recent happened 640,000 years ago. Yellowstone's volcanism is powered by magma rising from a hotspot.
A biased opinion is based on a preconceived notion or idea about a thing, person or group of people based on personal beliefs. In psychology, a bias is known as a cognitive shortcut.. It is based on the idea that the human brain, in order to conserve energy, naturally looks for shorter paths to conclusions by using what has been ingrained to draw speedy conclusions.
Bias is a systematic error that leads to an incorrect estimate of effect or association. Many factors can bias the results of a study such that they cancel out, reduce or amplify a real effect you are trying to describe. Epidemiology categorises types of bias, examples are: