Trihalomethanes (or THM’s) refers to a broad class of organic compounds, including chloroform and bromoform. Many THM’s are known or suspected human carcinogens, and, because they are a biproduct of disinfection in water treatment facilities, their concentrations in drinking water are regulated by federal law. Four measurements of THM levels in drinking water yielded the following results, in parts per billion (ppb): 48, 65, 72, and 70. Assume that we know, from other drinking water quality surveys, that THM concentrations of this magnitude tend to be roughly normally distributed. (a) What is the mean THM concentration for this sample of four measurements? (b) What is the standard deviation of the sample and what is the standard error of the mean? (c) What is the 95% (two-tailed) confidence interval for the mean?
Unitary Method
The word “unitary” comes from the word “unit”, which means a single and complete entity. In this method, we find the value of a unit product from the given number of products, and then we solve for the other number of products.
Speed, Time, and Distance
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Profit and Loss
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Units and Measurements
Measurements and comparisons are the foundation of science and engineering. We, therefore, need rules that tell us how things are measured and compared. For these measurements and comparisons, we perform certain experiments, and we will need the experiments to set up the devices.
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Trihalomethanes (or THM’s) refers to a broad class of organic compounds, including chloroform and bromoform. Many THM’s are known or suspected human carcinogens, and, because they are a biproduct of disinfection in water treatment facilities, their concentrations in drinking water are regulated by federal law. Four measurements of THM levels in drinking water yielded the following results, in parts per billion (ppb): 48, 65, 72, and 70. Assume that we know, from other drinking water quality surveys, that THM concentrations of this magnitude tend to be roughly
normally distributed. -
(a) What is the
mean THM concentration for this sample of four measurements? -
(b) What is the standard deviation of the sample and what is the standard error of the mean?
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(c) What is the 95% (two-tailed) confidence interval for the mean?
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(d) What is the 95% prediction interval for the individual measurements? That is, what interval encloses 95%
of all possible data, given the mean and standard deviation that you have calculated?
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Given that,
Four measurements of THM levels in drinking water yielded the following results, in parts per billion (ppb): 48, 65, 72, and 70.
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