a. Determine and interpret a 99% lower confidence bound for the mean cadmium level of all Boletus pinicola mushrooms. b. Compare your one-sided confidence interval in part (a) to the (twosided) confidence interval found in Exercise 8.71.
Another type of confidence interval is called a one-sided confidence interval. A one-sided confidence interval provides either a lower confidence bound or an upper confidence bound for the parameter in question. You are asked to examine one-sided confidence intervals in Exercises.
Exercise
Toxic Mushrooms? Refer to Exercise 8.71.
a. Determine and interpret a 99% lower confidence bound for the mean cadmium level of all Boletus pinicola mushrooms.
b. Compare your one-sided confidence interval in part (a) to the (twosided) confidence interval found in Exercise 8.71.
Reference 8.71
Toxic Mushrooms? Cadmium, a heavy metal, is toxic to animals. Mushrooms, however, are able to absorb and accumulate cadmium at high concentrations. The Czech and Slovak governments have set a safety limit for cadmium in dry vegetables at 0.5 part per million (ppm). M. Melgar et al. measured the cadmium levels in a random sample of the edible mushroom Boletus pinícola and published the results in the paper “Influence of Some Factors in Toxicity and Accumulation of Cd from Edible Wild Macrofungi in NW Spain (Journal of Environmental Science and Health, Vol. B33(4), pp. 439455). Here are the data obtained by the researchers.
| 0.24 | 0.59 | 0.62 | 0.16 | 0.77 | 1.33 |
| 0.92 | 0.19 | 0.33 | 0.25 | 0.59 | 0.32 |
Find and interpret a 99% confidence interval for the mean cadmium level of all Boletus pinicola mushrooms. Assume a population standard deviation of cadmium levels in Boletus pinicola mushrooms of 0.37 ppm. (Note: The sum of the data is 6.31 ppm.)
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