In a manufacturing process, the impurity level of the product is measured on a daily basis. When the process is operating normally, the impurity level is approximately normally distributed with a mean value of 0.800% and a standard deviation of 0.021%. The laboratory measurements for a period of eight consecutive days are shown below. From an SPC perspective is there strong evidence to believe that the mean value of the impurity has shifted? Justify youranswer.

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Impurity (%) 0.799 0.833 0.815 0.807 Day Impurity (%) 0.812 0.791 0.841 0.814 Day 1. 6. 4