Joan's nursery specializes in custom-designed landscaping for residential areas. the estimated labor cost associated with a particular landscaping proposal is based on the number of plantings of trees, shrubs, and so on to be used for the project. for cost estimating purposes, managers use hours of labor time for the planting of a medium-sized tree. actual times from a sample of plantings during the past month follow (times in hours).

1.7 1.5 2.6 2.2 2.4 2.3 2.6 3.0 1.4 2.3

with a level of significance, test to see whether the mean tree-planting time differs from hours.

(a) state the null and alternative hypothesis
(b) compute the sample mean