I believe the evidence is overwhelming that the Ashkenazic Jews are the most intelligent ethnic group on the planet. Their average IQ is 115. The average for non-Jewish white people is 100, for asians it is 109, for African-Americans it is 85, and for native Africans it is 70.
The word stupid can be defined in a variety of ways. In terms of IQ, I believe it is fair to say that a person with an IQ below 85 is stupid. Defining stupidity in this manner is somewhat arbitrary, in the same way as defining a genius as a person with an IQ above 130. Based on IQ, there are very few stupid Jews.
Among the non-Jews (goyim), the percentage of stupid people varies depending upon which group of non-Jews you are studying. It is false to say that all non-Jews are stupid. For example, I am not Jewish, and I am not stupid.
Here is an interview with an 11 year old Jewish prodigy on the subject of Jewish intelligence: SOME THOUGHTS ABOUT JEWS, IQ AND NOBEL LAUREATES