Translation of Stichprobe

I need to write you one more sentence. This is what my teacher told me and the German language is so difficult. So please, as a last favor, would you please write the sentence for me in German?
The belief of somebody that a race or a group of people to which he belongs is superior to another. Even though the word itself stems from the word 'race', its meaning must be generalized.
On the way we met a nice village girl which tried to sell us some souvenirs. We told her that we would not buy from her. Her English was excellent, and we did not believe that she was twelve years old.