Raising pay. A school system employs teachers at salaries between

$30,000 and $60,000. The teachers’ union and the school board are negotiating the form of next year’s increase in the salary schedule. Suppose that every teacher is given a flat $1000 raise.

(a) How much will the mean salary increase? The median salary?

(b) Will a flat $1000 raise increase the spread as measured by the distance between the quartiles? Explain.

(c) Will a flat $1000 raise increase the spread as measured by the standard deviation of the salaries? Explain. (See Exercise 12.27 if you need help.)