typos ch 8.2.1

[lbersh]

Current: "You may remember from algebra that a line is define as follows:"
Should read: "You may remember from algebra that a line is defined as follows:"

Current: "we also call the intercept, since it maps onto the intercept in the equation for a line."
Should read: "we also call it the intercept, since it maps onto the intercept in the equation for a line."

Current: "...and only very slighly better by including gender as well."
Should read: "...and only very slightly better by including gender as well."