Question

ANSWER ALL OF THEM IT IS ONE QUESTION PLEASE.

9.2.20 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.

1. Identify the observational units.
2. Is this an experiment or an observational study? How are you deciding?
3. Identify the explanatory and response variable. Also, for each variable, identify whether categorical or quantitative.
4. State the appropriate null and alternative hypotheses in words.
5. State the appropriate null and alternative hypotheses in symbols. Be sure to define the symbols used.

6. The p-value is 0.0034. We have strong evidence of an association between wing length and flight time.

   True OR   False

7. The p-value is 0.0034. The results suggest a cause-and-effect relationship.

   True OR  False

8. The p-value is 0.0034. The results can be generalized beyond these particular helicopters.

   True OR   False

9. The sample sizes are less than 20, but the data in each group are reasonably symmetric. The SDs are within a factor of 2 of each other. So the validity conditions are all met for this data set.

   True OR. False

10. A follow-up analysis is appropriate, to determine how much the flight times vary.

    True OR. False

11. It is important to make all other aspects of the helicopters identical so that the difference in flying time can be attributed to wing length and no other factors. Any other differences in the helicopters could also be explaining the difference in flying times.

    True OR False

Answer 1

1. Observational Units: Flight Time in seconds, Wing length

2. This is observational study. In this study the researcher simply observes the subjects without interfering.

3. Wng Length is explanatory variable and flight type is response variable

4. The Null Hypothesis is the mean flight time is independent of the wing length of the helicopter

5. Let is the flight time in seconds for wing size 3 cm

11

and is the flight time in seconds for wing size 2 cm

112

$H_0: \mu_1 = \mu_2$

$H_1: \mu_1 \ne \mu_2$

6. Since p-value is < 0.05, we reject the Null Hypothesis. Answer is True

7. True

8. False, The sample size too small to assume a normal ditribution

9. True

10. True