Radioactive lichen. Refer to the Lichen Radionuclide Baseline Research project at the University of Alaska, presented in Exercise 2.196

(p. 136). Recall that the researchers collected 9 lichen specimens and measured the amount (in microcuries per milliliter) of the radioactive element cesium-137 for each.

(The natural logarithms of the data values are saved in the LICHEN file.) A MINITAB printout with summary statistics for the actual data is shown below.

a. Give a point estimate for the mean amount of cesium in lichen specimens collected in Alaska.

b. Give the t-value used in a small-sample 95% confidence interval for the true mean amount of cesium in Alaskan lichen specimens.

c. Use the result you obtained in part b and the values of x and s shown on the MINITAB printout to form a 95%
confidence interval for the true mean amount of cesium in Alaskan lichen specimens.

d. Check the interval you found in part c with the 95%
confidence interval shown on the MINITAB printout.

e. Give a practical interpretation for the interval you obtained in part c.

f. Suppose the researchers want to increase the sample size in order to estimate the mean m to within .001 microcurie per milliliter of its true value, using a 95% confidence interval. Compute the sample size necessary to obtain the desired estimate.

Transcribed Image Text:

Mean 9 0.009027 Variable N CESIUM StDev 0.004854 SE Mean. 0.001618 95% CI (0.005296, 0.012759)