2. A 23 experiment with two replicates in blocks was performed to study the flight time of paper helicopters. The design variables and their levels are shown in the following table. The width and length variables refer to the blade geometry and the folds variable indicates the number of one inch folds in the helicopter's bottom leg. The run order was randomized within each block. Variable -1 +1 Units A: Width 1.25 2 inch B: Length 2 C: Folds 4 inch 1 2 NA The experimental flight times were measured in seconds and are reported below. Analyze the data and include a term for blocks in the model. What helicopter geometry is predicted to give maximum flight time? Extrapolate your model to recommend another helicopter geometry that would give even longer flight time. What are the risks associated with this recommendation? B|C - + + Block 1 2 2.99 2.90 2.99 2.99 - 5.13 5.58 + + 5.21 5.41 + 2.82 2.93 + + 2.95 2.62 + + - 4.41 4.62 + + + 4.39 4.97 5-

Fig: 1