The singular mistake: understanding why "criteria was" is incorrect

What kind of error is it?

This is a grammatical error related to subject-verb agreement.

Why do people make this mistake?

People often make this error because "criteria" is commonly mistaken for a singular noun when it is actually the plural form of "criterion". In English, nouns ending in "-a" are often perceived as singular, leading to confusion.

What is correct?

The correct usage is "criteria were" since "criteria" is the plural of "criterion" and requires a plural verb.