The Environmental Protection Agency is concerned with the problem of setting criteria for the amounts of certain toxic chemicals to be allowed in freshwater lakes and rivers. A common measure of toxicity for any pollutant is the concentration of the pollutant that will kill half of the test species in a given amount of time (usually 96 hours for fish species). This measure is called LC50 (lethal concentration killing 50% of the test species). In many studies, the values contained in the natural logarithm of LC50 measurements are normally distributed, and, hence, the analysis is based on In(LC50) data. Suppose that n = 30 observations are to be taken on In(LC50) measurements and that o² = 1.7. Let S² denote the sample variance of the 30 measurements. (a) Find a number b such that P(S² ≤ b) = 0.975. (Round your answer to three decimal places.) b = (b) Find a number such that P(a ≤ S²) = 0.975. (Round your answer to three decimal places.) a = (c) If a and b are as in parts (a) and (b), what is P(a ≤ s² ≤ b)? (Round your answer to two decimal places.) P(a ≤ s² ≤ b) =

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The Environmental Protection Agency is concerned with the problem of setting criteria for the amounts of certain toxic chemicals to be allowed in freshwater lakes and rivers. A common measure of
toxicity for any pollutant is the concentration of the pollutant that will kill half of the test species in a given amount of time (usually 96 hours for fish species). This measure is called LC50 (lethal
concentration killing 50% of the test species). In many studies, the values contained in the natural logarithm of LC50 measurements are normally distributed, and, hence, the analysis is based on
In(LC50) data.
Suppose that n = 30 observations are to be taken on In(LC50) measurements and that o
0² = 1.7. Let S² denote the sample variance of the 30 measurements.
(a) Find a number b such that P(S² ≤ b) = 0.975. (Round your answer to three decimal places.)
b =
(b) Find a number a such that P(a ≤ S²) = 0.975. (Round your answer to three decimal places.)
a =
(c)
If a and b are as in parts (a) and (b), what is P(a ≤ S² ≤ b)? (Round your answer to two decimal places.)
P(a ≤ S² ≤ b) =
Transcribed Image Text:The Environmental Protection Agency is concerned with the problem of setting criteria for the amounts of certain toxic chemicals to be allowed in freshwater lakes and rivers. A common measure of toxicity for any pollutant is the concentration of the pollutant that will kill half of the test species in a given amount of time (usually 96 hours for fish species). This measure is called LC50 (lethal concentration killing 50% of the test species). In many studies, the values contained in the natural logarithm of LC50 measurements are normally distributed, and, hence, the analysis is based on In(LC50) data. Suppose that n = 30 observations are to be taken on In(LC50) measurements and that o 0² = 1.7. Let S² denote the sample variance of the 30 measurements. (a) Find a number b such that P(S² ≤ b) = 0.975. (Round your answer to three decimal places.) b = (b) Find a number a such that P(a ≤ S²) = 0.975. (Round your answer to three decimal places.) a = (c) If a and b are as in parts (a) and (b), what is P(a ≤ S² ≤ b)? (Round your answer to two decimal places.) P(a ≤ S² ≤ b) =
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