People can draw bad conclusions and made bad choices. And if it combines with low competence Dunning–Kruger emerge: people can't be aware of their own errors due to the lack of competence. As a result people tend to overestimate their own skills and knowledge when it is on the low level. Such a person also tends to incorrectly estimate the level of skill of another person.
J. Ehrlinger, K. Johnson, M. Banner, D. Dunning, J. Kruger, “Why the unskilled are unaware”, Organizational Behavior and Human Decision Processes 105 (2008).