Question

Q.4

A group of researchers wants to estimate the true mean skidding distance along a new road in a certain forest. The skidding distances? (in meters) were measured at 20 randomly selected road sites. These values are given in the accompanying table. Complete parts a through d.

485	351	459	199	288	408	574        439        546     385
298	430	184	263	272	403	310        312         141   426

a. Estimate the true mean skidding distance for the road with a 90?% confidence interval. ------, ------?

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

The confidence interval means that we are ------?% confident that the true Select from bellow =

?

(Skidding distance variance) OR (Mean skidding distance) OR (Skidding distance standard deviation for

?

(The whole road )OR (the sampled points ) is in the interval.

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

A. The sample size must be much smaller than the population size.

B. The population distribution must be approximately normal.

C. The sample must be randomly selected from the population.

D. The sample must be selected carefully to represent the whole population.

Is it reasonable to assume that the population distribution is approximately? normal?

A. Yes, because the sample distribution is approximately normal.

B. The condition does not apply.

C. No, because the sample distribution is definitely not normal.

Is it reasonable to assume that the sample is? random?

A. Yes, because the problem statement indicates that it is.

B. The condition does not apply.

C. No, because we do not know the methods used by the researchers.

Is it reasonable to assume that the sample size is much smaller than the population? size?

A. The condition does not apply.

B. No, because the length of the road is unknown.

C. Yes, because there are many points that could be chosen along the road.

Is it reasonable to assume that the sample was selected carefully to represent the whole? population?

A. Yes, because the problem statement indicates that it was.

B. The condition does not apply.

C. No, because we do not know the methods used by the researchers.

d. A logger working on the road claims the mean skidding distance is at least 434 meters. Do you? agree?

Select from below

(Yes OR No), because the value 434 lies (Outside OR inside) the confidence interval.

Answer 1