Data on the Water Quality in the Eastern United States

Multiple Choice

Data on the water quality in the eastern United States were obtained by a researcher who wanted to ascertain whether the amount of particulates in water (ppm) could be used to accurately predict the water quality score. Suppose we use the following simple linear regression model:
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Quality_i = α+ β× particulates_i + Ɛ_i
Where the deviations Ɛ_i are assumed to be independent and Normally distributed with mean 0 and standard deviation σ. This model was fit to the data using the method of least squares. The following results were obtained from statistical software based on a sample of size 61:

$$\begin{array} { | l | c | c | } \hline \text { Variable } & \text { Estimate } & \begin{array} { c } \text { Standard Error of } \\\text { Estimate }\end{array} \\\hline \text { Constant } & 6.214 & 1.003 \\\text { Particulates } & - 0.009 & 0.020 \\\hline\end{array}$$
r² = 0.005, s = 0.7896.
Here is a scatterplot of the amount of particulates versus water quality:
Which of the following statements is supported by the plot?

A) There is no striking evidence in the plot suggesting that the assumptions for regression are violated.
B) There appears to be a serious outlier in the plot, suggesting that our results must be interpreted with caution.
C) The plot contains dramatic evidence that the standard deviation of the response about the true regression line is not approximately the same everywhere.
D) The plot contains many fewer points than were used to fit the least-squares regression line in the previous problems.Obviously, there is a major error present.