2. Paper helicopters can be cut from one half of an 8 1/2 * 11 sheet of paper as shown below.

These helicopters can be made quickly and inexpensively, and can be used to demonstrate experimental design concepts. An experiment can be per-
formed by constructing a helicopter, dropping it from a xed height, and clocking the time it takes to rotate to the oor, as shown below, with a stopwatch. The wing length could be varied by trimming some paper o the top prior to folding the wings. Trimming some paper o would reduce the weight of the helicopter, but would also result in less surface area on the blades. You could experiment to determine if changing the wing length aects the ight time.

(a) Describe the experimental unit.

(b) Explain the dierence in replicates and duplicates for this situation.

(c) Describe the treatment factor.

(d) Describe any lurking variables that might aect the results of experi-
ments.

(e) Explain why randomization would be important.

(f) Create a randomized list of experiments for examining four wing lengths of (4", 4.75", 5.5" and 6") with eight replicate experiments in each level.
(g) Carry out the experiments and collect the data.
(h) Perform an analysis of variance with your data.
(i) Check the equal variance and normality assumptions with residual plots.
(j) Test whether there is a signicant linear or quadratic trend in ight times as the wing length increases.

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