1. If 5, 8, 6, and 2 occur with frequencies 3, 2, 4, and 1, respectively, the arithmetic mean is
2. If a final examination in a course is weighted 3 times as much as a quiz and a student has a final examination grade of 85 and quiz grades of 70 and 90, the mean grade is
3. The deviations of the numbers 8, 3, 5, 12, and 10 from their arithmetic mean 7.6 are 8 - 7.6, 3 - 7.6, 5 - 7.6, 12 - 7.6, and 10 - 7.6, or 0.4, -4.6, -2.6, 4.4, and 2.4, with algebraic sum 0.4 - 4.6 - 2.6 + 4.4 + 2:4 = 0.
4. The sum of the squares of the deviations of a set of numbers Xj from any number a is a minimum if and only if a =