I have an open ended question in a textbook:
A teaching assistant gives a quiz. There are 10 questions on the quiz and no partial credit is given. After grading the papers the TA writes down for each student the number of questions the student got right and the number wrong. What is the correlation of the number of questions right and wrong? Hint: Make up some data for number of questions right, calculate number of questions wrong, and plot them against each other.
I don't get it.
So it seems like the two are inversely correlated (less than 0), but I don't get how to calculate it just based on number of right and wrong. What am I missing?
Additionally, how do you calculate R (correlation) from this data?
