User experience professionals salary survey. The User Experience Professionals Association (UXPA) supports people who research, design, and evaluate the user experience of products and services. The UXPA periodically conducts a salary survey of its members (e.g., UXPA Salary Survey, November 2018). Each year, one of the authors of the report (Jeff Sauro) employs multiple regression to find the factors that have the greatest influence on a professional’s salary. In 2018, Sauro reported that region of the country explained the most variation (36%) in salary. In 2014, Sauro fit a first-order multiple regression model for salary (y, in dollars) as a function of years of experience 1x12, 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: yn = 52,484 + 2,941x1 + 16,880x2 + 11,108x3

a. Predict the salary of a UXPA member with 10 years of experience, who does not have a PhD, but is a manager.

b. Predict the salary of a UXPA member with 10 years of experience, who does have a PhD, but is not a manager.

c. Why is a 95% prediction interval preferred over the predicted values given in parts a and b?