Elementary Statistics 7th.ed. Instructor's Review Copy

7th Edition

ISBN: 9780134683584

Author: Larson

Publisher: PEARSON

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Textbook Question

Chapter 6, Problem 3RSRD

The Safe Drinking Water Act, which was passed in 1974, allows the Environmental Protection Agency (EPA) to regulate the levels of contaminants in drinking water. The EPA requires that water utilities give their customers water quality reports annually. These reports include the results of daily water quality monitoring, which is performed to determine whether drinking water is safe for consumption.

A water department tests for contaminants at water treatment plants and at customers laps. These contaminants include microorganisms, organic chemicals, and inorganic chemicals such as cyanide. Cyanide’s presence in drinking water is the result of discharges from Steel, plastics, and fertilizer factories. For drinking water, the maximum contaminant level of cyanide is 0.2 part per million.

As part of your job for your city’s water department, you are preparing a report that includes an analysis of the results shown in the figure at the right. The figure shows the point estimates for the population mean concentration and the 95% confidence intervals for μ for cyanide over a three-year period. The data are based on random water samples taken by the city’s three water treatment plants.

Chapter 6, Problem 3RSRD, The Safe Drinking Water Act, which was passed in 1974, allows the Environmental Protection Agency

3. What Do You Think?

The confidence interval for Year 2 is much larger than the other years. What do you think may have caused this larger confidence level?

Definition Definition Measure of central tendency that is the average of a given data set. The mean value is evaluated as the quotient of the sum of all observations by the sample size. The mean, in contrast to a median, is affected by extreme values. Very large or very small values can distract the mean from the center of the data. Arithmetic mean: The most common type of mean is the arithmetic mean. It is evaluated using the formula: μ = 1 N ∑ i = 1 N x i Other types of means are the geometric mean, logarithmic mean, and harmonic mean. Geometric mean: The nth root of the product of n observations from a data set is defined as the geometric mean of the set: G = x 1 x 2 ... x n n Logarithmic mean: The difference of the natural logarithms of the two numbers, divided by the difference between the numbers is the logarithmic mean of the two numbers. The logarithmic mean is used particularly in heat transfer and mass transfer. ln x 2 − ln x 1 x 2 − x 1 Harmonic mean: The inverse of the arithmetic mean of the inverses of all the numbers in a data set is the harmonic mean of the data. 1 1 x 1 + 1 x 2 + ...

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Chapter 6, Problem 2RSRD

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Chapter 6 Solutions

Elementary Statistics 7th.ed. Instructor's Review Copy

Ch. 6.1 - In Example 1, the researcher selects a second...Ch. 6.1 - Use the data in Try It Yourself 1 and a 95%...Ch. 6.1 - Use the data in Try It Yourself 1 to construct a...Ch. 6.1 - Use the data in Example 1 and technology to...Ch. 6.1 - Construct a 90% confidence interval for the...Ch. 6.1 - In Example 6, how many student-athletes must the...Ch. 6.1 - When estimating a population mean, are you more...Ch. 6.1 - Which statistic is the best unbiased estimator for...Ch. 6.1 - For the same sample statistics, which level of...Ch. 6.1 - You construct a 95% confidence interval for a...

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Solution Summary: The author explains why the confidence interval for Year 2 is larger than the other years because cyanide's presence in drinking water is the result of discharges from steel, plastics, and fertilizer factories.

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