Similar to the fundamental attribution error, in this error a person is likely to make an internal attribution to an entire group instead of the individuals within the group.
The ultimate attribution error is the tendency to explain negative behaviours of an out-group member as a flaw in their personality, and to justify positive behaviour performed by an out group member as a result of uncommon circumstances . It is also the belief that positive acts performed by in group members are a result of their personality, whereas if an in group member behaves negatively this is believed to be rare, and a result of situational factors
Examples: Little old ladies are assumed to be kind, Jews assumed avaricious, children assumed to be innocent, etc. (of course, these are not true)