Dunning-Kruger effect
Behavioural economics.
The Dunning-Kruger effect is an irrational tendency among certain incompetent individuals systematically to overestimate their true level of competence.
In simple terms, the Dunning-Kruger effect is the reverse of the Impostor syndrome.
A possible explanation for the Dunning-Kruger effect is that the skills we need to assess our level of task competence correctly, are exactly the same skills that we need to perform the task itself. Those lacking in one of these sets of skills would then, by definition, lack the other set of skills too.
The Dunning-Kruger effect can be 'cured' with even a relative moderate amount of appropriate training.
Such tendencies to assess evidence incorrectly are known collectively as 'cognitive bias'.