A manager of boiler drums wants to use regression analysis to predict the number of worker-hours needed to erect the drums in future projects. Data for 36 randomly selected boilers have been collected. In addition to worker-hours (Y), the variables measured include boiler capacity, boiler design pressure, boiler type, and drum type. All of these measurements are listed in the file P10_27.xlsx.
a. Estimate an appropriate multiple regression equation to predict the number of worker-hours needed to erect boiler drums.
b. Interpret the estimated regression coefficients.
c. According to the estimated regression equation, what is the difference between the mean number of worker-hours required for erecting industrial and utility field boilers?
d. According to the estimated regression equation, what is the difference between the mean number of worker-hours required for erecting boilers with steam drums and those with mud drums?
e. Given the estimated regression equation, predict the number of worker-hours needed to erect a utility-field, steam-drum boiler with a capacity of 550,000 pounds per hour and a design pressure of 1400 pounds per square inch. How accurate is your prediction?
f. Given the estimated regression equation, predict the number of worker-hours needed to erect an industrial-field, mud-drum boiler with a capacity of 100,000 pounds per hour and a design pressure of 1000 pounds per square inch. How accurate is your prediction?