Correct, except that if the choice of being Jewish is no longer one of the 20 choices provided, it will skew the result in the same manner in which the result would be skewed if Italian or Scottish was no longer included. The results of any questionnaire is largely dependent on the questions being asked and upon the format in which they are asked. 
The issue here appears to be that for some reason Jewish was deleted from the multiple choice examples, and this seems strange.