Sentence:  Since "px"(0), "px"(1), "py"(0) and "py"(1) are all equal to 1/2, knowing only px and py yields no information on "ε" whatsoever. You have to be a student at <WSD>Hogwarts</WSD> to be able to get the values of "p" right! 
Meaning of the word marked with <WSD> tags:  The Hogwarts School of Witchcraft and Wizardry, a school for learning magic in (J.K. Rowling)'s "(Harry Potter)" series of books.