Your textbook states that correlation of the error term across observations "will not happen if the data are obtained by sampling at random from the population." However,in one famous study of the electric utility industry,the observations were listed by the size of the output level,from smallest to largest.The pattern of the residuals was as shown in the figure. 
What does this pattern suggest to you?
Definitions:
Duress
involves the use of force, threat, or coercion to compel someone to act against their will or judgment.
Undue Influence
The improper use of power or trust in a way that deprives a person of free will and substitutes another's objective.
Workpapers
Documentation that records the procedures, tests, and results of an audit, serving as support for the auditor's conclusion.
Appeal
The process of asking a higher court to review and change the decision of a lower court.
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