<p>1) One of the more challenging problems confront the water pollution control field is presented by the tanning industry. Tannery wastes are chemically complex. The following computer printout is based on 33 random samples of chemically treated waste to predict the percent of chemical oxygen demand based on the perent of chemical solid reduction. </p>
<p>Predictor Constant –> 3.830 (Coef), 1.768 (Stdev), 2.17 (t-ratio), .038 (p)
% Reduc –> 0.90364 (Coef), 0.05012 (Stdev), 18.03 (t-ratio), 0.000 (p)
s=3.230, R-sq=91.3%</p>
<p>a) Test to see if there is a linear relationship for a 1% level of significance.
b) What is the standard error of the slope? Interpret.
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2) The growth and decline of forests is a matter of great public and scientific interest. The paper “Relationships Among Crown Condition, Growth, and Stand Nutriotion in Seven Northern Vermont Sugarbushes” included a scatter plot of y = mean crown dieback (%), which is one indicator of growth retardation, and x = soil pH. A statistical computer package MINITAB gives the following analysis: </p>
<p>Predictor Constant –> 31.040 (Coef), 5.445 (Stdev), 5.70 (t-ratio), 0.000 (p)
soil ph –> -5.792 (Coef), 1.363 (Stdev), -4.25 (t-ratio), 0.001 (p)
s = 2.981, R-sq = 51.5%</p>
<p>a) What is the correlation coefficient? Interpret.
b) What is the slope? Interpret in terms of the problem.</p>