Your Coworker Has Run a Simple Univariate Regression and Computed $Y = \sum _ { t = 1 } ^ { n } \left( \hat { Y } _ { t } - \bar { Y } \right) ^ { 2 } = 550$

Essay

Your coworker has run a simple univariate regression and computed the explained and the total variation in Y and asked you to compute the coefficient of correlation Expl.var.in $Y = \sum _ { t = 1 } ^ { n } \left( \hat { Y } _ { t } - \bar { Y } \right) ^ { 2 } = 550$
Total. var.in $Y = \sum _ { t = 1 } ^ { n } \left( Y _ { t } - \bar { Y } \right) ^ { 2 } = 895$