When planning for a new forest road to be used for tree harvesting, planners must select the location to minimize tractor skidding distance. In the Journal of Forest Engineering, researchers wanted to estimate the true mean skidding distance along a new road in a European forest. The skidding distances (in meters) were measured at 20 randomly selected road sites. These values are given in the accompanying table.

a. Estimate the true mean skidding distance for the road with a 95% confidence interval.

b. Give a practical interpretation of the interval, part a.

c. What conditions are required for the inference, part b, to be valid? Are these conditions reasonably satisfied?

d. A logger working on the road claims the mean skidding distance is at least 425 meters. Do you agree?

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435 574 439 546 312 141 425 488 350 457 199 285 409 385 295 184 261 273 400 311