Assume that the differences are normally distributed. Complete parts (a) through (d) below. Observation 1 2 3 4 5 6 7 8 Xi 45.8 48.2 46.5 43.0 50.7 47.8 48.9 54.6 47.5 46.4 49.7 48.2 52.2 51.9 52.5 54.1 b) Compute d and Sg. d = - 2.125 (Round to three decimal places as needed.) "Round to three decimal places as needed.)