Betty and Tina, both third-graders in the same classroom, are assigned by their teacher to different groups that will compete in a spelling bee. Betty and Tina each believe that their own group is composed of the better spellers. The girls' beliefs best illustrates

Answer: Ingroup bias

Explanation:

Ingroup bias is defined as the tendency in which a person tends to favor their own group and ignore other groups traits. Group members, traits and results of own group drags a person to favor their group instead of analyzing other group's performance.

According to the question, believe of Tina and Betty is based on ingroup bias due to which they think that their own groups have better members who are skilled at spelling. They are favoring their own group over other group.