A pollution-control inspector suspected that a riverside community was releasing
ID: 3390995 • Letter: A
Question
A pollution-control inspector suspected that a riverside community was releasing semi-treated sewage into a river and this, as a consequence, was changing the level of dissolved oxygen of the river. To check this, he drew 15 randomly selected specimens of river water at a location above the town and another 15 specimens below. The sample information and the QQplots by groups are given blow.
1. Use the Wilcoxon Rank-Sum method to test for a difference between the distributions at ?=0.05. Give the p-value and conclusion.
2. Which test (two-sample t or Wilcoxon Rank-Sum test) is appropriate? Justify your response.
Important: Do not use Rcmdr to solve this problem!
mean sd n Above 4.92 0.1567528 15 Below 4.74 0.3202677 15 Above Below o o o norm quantiles norm quantilesExplanation / Answer
A pollution-control inspector suspected that a riverside community was releasing
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