The slope of this line is . Suppose that the P in this equation refers to the price of a magazine subscription, and the Q refers to the number of magazine subscriptions sold. Read the following statement carefully: "When the price of a magazine subscription goes up, fewer people subscribe to the magazine." Which of the following best summarizes the pattern of causality suggested by this statement? A change in P causes a change in Q . The relationship between P and Q is not a causal relationship. A change in Q causes a change in P