In June 2002, chemical analyses of n_1 = 110 water samples from various parts of

Question

In June 2002, chemical analyses of n_1 = 110 water samples from various parts of Catawba river were made. One objective was to measure the mean chlorine content of the water in this river. During the next two winters, the use of road salt was substantially increased. In June of 2004, the experiment was repeated using n_2 = 85 water samples. The findings are summarized in the following table. Set up the null and alternative hypotheses to test whether the mean chlorine content in the river has increased. A) H_0:u_1 > u_2 vs H_a:u_1

Explanation / Answer

1) Hypothesis:

Ho : mu1 = mu2 vs Ha: mu1 > mu2

2) n1 = =110 , n2 = 85 , x1 = 17.8 , x2 = 18.3 , s1 = 1.8 , s2 = 1.2

SE = sqrt [(s12/n1) + (s22/n2)]
SE = sqrt [(1.8^2 / 110) + (1.2^2/85)]

= 0.215

t = [ (x1 - x2) - d ] / SE

= [(17.8 - 18.3) - 0] / 0.215

= -2.32

Answer Option a)

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