Final answer:
The consequence described in the question is illusory correlation, where Billy forms the belief that all Russian immigrants are thieves based on one instance of a Russian immigrant robbing a jewelry store.
Step-by-step explanation:
The consequence described in the question is illusory correlation. Illusory correlation refers to the tendency to perceive a relationship between two variables that are unrelated or only weakly related. In this case, Billy forms the belief that all Russian immigrants are thieves based on one instance of a Russian immigrant robbing a jewelry store. This is an example of illusory correlation because it assumes a correlation between Russian immigrants and criminal behavior based on limited and unrelated information. It is important to recognize that individuals should not make generalizations or form stereotypes about an entire group based on the actions of a few individuals.