In a study of the effect of wing length on the flight time of paper helicopters, two wing lengths were of interest: 2 cm and 3 cm. Two paper helicopters were made, one with a wing length of 2 cm and the other with 3 cm. All other aspects of the helicopters were made to be as identical as possible. Each helicopter was repeatedly dropped from a height of 10 feet and flight time was measured in seconds taken for the helicopter to hit the ground.

a. Identify the observational units.

b. Is this an experiment or an observational study? How are you deciding?
c. Identify the explanatory and response variable. Also, for each variable, identify whether categorical or quantitative.
d. State the appropriate null and alternative hypotheses in words.
e. State the appropriate null and alternative hypotheses in symbols. Be sure to define the symbols used. The data file is FlightTimes.
f. Use technology (either an applet or statistical soft ware) to implement a two-sample t-test to test whether the flight times differ significantly for the two wing lengths. Report the mean, SD, and sample size of each group. Also, report the t-statistic as well as a p-value. Recall that the t-test is the theory-based test for comparing two groups
on a quantitative response.
g. Now, use technology (either an applet or statistical software) to implement the ANOVA test to test whether the flight times diff er significantly for the two wing lengths. Be sure to report the F-statistic and the corresponding p-value.
h. Compare the two p-values reported in parts (f) and (g). Are they about the same or different?
i. State an appropriate conclusion in the context of the study. Be sure to comment on statistical significance, causation, and generalization along with how you are making your decision.
j. State the conditions under which the results from the theory-based ANOVA test would be valid. In the context of this study, is it valid to use the ANOVA test? Explain how you are deciding.
k. If appropriate, perform follow-up analysis. If you do not think follow-up analysis is appropriate, explain why not.
l. Why is it important to state that “All other aspects of the helicopters were made to be as identical as possible”?