Z-score article and practice:
https://www.thoughtco.com/z-scores-worksheet-solutions-3126533
https://www.khanacademy.org/math/ap-statistics/density-curves-normal-distribution-ap/measuring-position/e/z_scores_1
https://www.superteachertools.us/jeopardyx/jeopardy-review-game.php?gamefile=153944#.Wy1G2S_MzOR
