11.35. The Paper Helicopter Experiment Revisited.

Reconsider the paper helicopter experiment in Problem 11.34.

This experiment was actually run in two blocks. Block 1 consisted of the first 16 runs in Table P11.11 (standard order runs 1–16) and two center points (standard order runs 25 and 26).

11.8 Problems 551

(a) Fit main-effects plus two-factor interaction models to the block 1 data, using both responses.

(b) For the models in part

(a) use the two center points to test for lack of fit. Is there an indication that secondorder terms are needed?

(c) Now use the data from block 2 (standard order runs 17–24 and the remaining center points, standard order runs 27–30) to augment block 1 and fit second-order models to both responses. Check the adequacy of the fit for both models. Does blocking seem to have been important in this experiment?

(d) What design would you recommend to maximize the flight time while simultaneously minimizing the standard deviation of flight time?