A statistician is doing a study on a group of undergraduates. On average, these students drink 4 beers a month, with an SD of 8. They eat 4 pizzas a month, with an SD of 4. There is some positive association between beer and pizza, and the regression equation is 13 predicted number of beers = $$\_\_\_\_$$ x number of pizzas + 2.

However, the statistician lost the data and forgot the slope of the equation.

(Perhaps he had too much beer and pizza.) Can you help him remember the slope? Explain. pl875