Skill Check 4 Solutions

x = 68.  z = (68 - 50)/10 = 1.8

z = -2.5   x = -2.5*10 + 50 = 25

From Table A in the book, 96.41% are less than 1.8 standard units, and so 100-96.41 = 3.59% scored higher than 68.

From Table A, to be in the top 5% your standard score must be z = 1.65 (or z = 1.64 would also be an acceptable choice).  So x = 1.65*10 + 50 = 66.5.