The Usability Professionals' Association (UPA) supports people who research, design, and evaluate the user experience of products and services. Recently, the UPA conducted a salary survey of its members (UPA Salary Survey, August IX, 2009). One of the report's authors, Jeff Sauro, investigated how much having a PhD affects salaries in this profession and discussed his analysis on the blog, www.measuringusability.com. Sauro fit a first-order multiple regression model for salary (y, in dollars) as a function of years of experience (x1), PhD status (x2 = 1 if PhD, 0 if not), and manager status (x3 = 1 if manager, 0 if not). The following prediction equation was obtained:
 = 52,484 + 2,941x1 + 16,880x2 + 11,108x3
a. Predict the salary of a UPA member with 10 years of experience who does not have a PhD, but is a manager.
b. Predict the salary of a UPA member with 10 years of experience who does have a PhD, but is not a manager.
c. The following coefficient was reported: R2a = .32. Give a practical interpretation of this value.
d. A 95% confidence interval for β1 was reported as (2700, 3200). Give a practical interpretation of this result.
e. A 95% confidence interval for β2 was reported as (11,500, 22,300). Give a practical interpretation of this result.
f. A 95% confidence interval for β3 was reported as (7.600, 14,600). Give a practical interpretation of this result.