12.48 Time levels of scale. Recall Exercise 7.62 (page 456). This experiment actually involved three groups. The last group was told the construction project would last 12 months. Here is a summary of the interval lengths (in days) between the earliest and latest completion dates.
| Group | n | s | |
|---|---|---|---|
| 1: 52 weeks | 30 | 84.1 | 55.8 |
| 2: 12 months | 30 | 104.6 | 70.1 |
| 3: 1 year | 30 | 139.6 | 73.1 |
(a) Is this an observational study or an experiment? Explain your answer.
(b) Use graphical methods to describe the three populations.
(c) Examine the conditions necessary for ANOVA. Summarize your findings.