The critical mind is a person who won't believe in somethng that contradicts other beliefs of this person. Apparenly such people make only 5% of general population. It means that the other 95% may be more or less easily persuaded that what they know as untrue is actually true. The critical minds can't be persuaded that what they they know as untrue is true. If they can be pesuaded, they are not critical minds.
It does not imply that people who believe that something is true and can't be persuaded that it is not are critical mind as well. Most likely they aren't since knowing that something false isn't symmetric with knowing that something is true. It is easier to disprove something than to prove that something is true. While the former is often possible the latter is often impossible. That's why the science progresses only by disproving things, then known as prejudices.