A product developer is interested in reducing the drying time of a primer paint. Two formulations of the paint are tested; formulation 1 is the standard chemistry, and formulation 2 has a new drying ingredient that should reduce the drying time.
From experience, it is known that the standard deviation of drying time is σ = 8 minutes, and this inherent variability should be unaffected by the addition of the new ingredient. Ten specimens are painted with formulation 1, and another 10 specimens are painted with formulation 2: the 20 specimens are painted in random order. The two sample average drying times are x1 = 121 minutes and x2 = 112 minutes, respectively.
1. What conclusions can the product developer draw about the effectiveness of the new ingredient, using α = 0.05?