If you enter the number of replicates, the power value, and the number of center points, Minitab calculates the effect. The effect is the difference in the response between the high and low levels of a factor that you want the design to detect. This difference is the result of one factor alone (main effect).
Use the effect size to determine the ability of the design to detect an effect. If you enter a number of replicates, a power, and a number of center points, then Minitab calculates the smallest effect size that the design can detect with the specified power. Usually, more replicates allow a designed experiment to detect smaller effects.
In these results, the design with one replicate can detect a difference of about 0.015 with 80% power. The difference that the design can detect with 90% power is larger than 0.015, about 0.018. The design with 2 replicates can detect a difference that is smaller than 0.015 with 80% power, about 0.007.
Power and Sample Size
α = 0.05 Assumed standard deviation = 0.01017
Factors: 31 Design: 32
Center pts (total): 4
Including a term for center points in model.
Points Reps Runs Power Effect
4 1 36 0.8 0.0153027
4 1 36 0.9 0.0180278
4 2 68 0.8 0.0073261
4 2 68 0.9 0.0084775