The article “Creep and Fatigue Characteristics of Ferrocement Slabs” (Journal of Ferroce...

The article “Creep and Fatigue Characteristics of Ferrocement Slabs” (Journal of Ferrocement [1984]: 309– 322) reported data on y = tensile strength (MPa), x₁ = slab thickness (cm), x₂ = load (kg), x₃ = age at loading (days), and x₄ = time under test (days) resulting from stress tests of n = 9 reinforced concrete slabs. The backward elimination method of variable selection was applied. Partial Minitab output follows. Explain what action was taken at each step in the process. Minitab output for the selected model is also given on page 14-29. Use the estimated regression equation to predict tensile strength for a slab that is 25 cm thick, 150 days old, and is subjected to a load of 200 kg for 50 days.