2nd Edition

ISBN: 9781259724275

Author: William Navidi, Barry Monk

Publisher: McGraw-Hill Education

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Chapter 15, Problem 3CS

Microorganisms play a crucial role in wastewater treatment by transforming solid organic matter into carbon dioxide and water In a wastewater treatment system, the solids retention time is average amount of time that solid organic matter resides in the treatment tank. A study was performed at the Colorado School of Mines to determine the relationship between the solids retention time and the diversity of the microorganism population. It was thought, because microorganisms feed on the solid matter, that longer retention times would provide more opportunity for genetic mutations to occur, resulting in a greater diversity of microorganisms.

Following are counts of the numbers of species of microorganism for retention times of 3 days, 12 days, and 30 days.

Chapter 15, Problem 3CS, Microorganisms play a crucial role in wastewater treatment by transforming solid organic matter into

Can you conclude at the α = 0.05 level that the median number of species for a retention time of 30 days differs from the median for a retention time of 12 days? Compute the appropriate test statistic, find the P-value, and state a conclusion.

Definition Definition Middle value of a data set. The median divides a data set into two halves, and it also called the 50th percentile. The median is much less affected by outliers and skewed data than the mean. If the number of elements in a dataset is odd, then the middlemost element of the data arranged in ascending or descending order is the median. If the number of elements in the dataset is even, the average of the two central elements of the arranged data is the median of the set. For example, if a dataset has five items—12, 13, 21, 27, 31—the median is the third item in ascending order, or 21. If a dataset has six items—12, 13, 21, 27, 31, 33—the median is the average of the third (21) and fourth (27) items. It is calculated as follows: (21 + 27) / 2 = 24.

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Chapter 15, Problem 2CS

Chapter 15, Problem 4CS

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Chapter 15 Solutions

Elementary Statistics 2nd Edition

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Solution Summary: The author analyzes whether the median number of species is greater for retention time of 30 days than for a retention period of 12 days. The hypothesis H0 is not rejected.

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