In this section we described control charts for R and x based on ranges. Control charts for monitoring variation and center (mean) can also be based on standard deviations. An s chart for monitoring variation is constructed by plotting sample standard deviations with a centerline at s (the mean of the sample standard deviations) and control limits at B4s and B3s, where B4 and B3 are found in Table 14-2 in this section. Construct an s chart for the data of Table 14-1. Compare the result to the R chart given in Example 3.
Answer to relevant QuestionsWhat is a voluntary response sample, and why is such a sample generally not suitable for a statistical study? A Gallup poll of 1018 adults reported that 39% believe in evolution. a. What is the exact value that is 39% of 1018? b. Could the result from part (a) be the actual number of adults who said that they believe in evolution? ...For each of the following, categorize the nature of the data using one of these three descriptions: (1) Discrete because the number of possible values is finite; (2) discrete because the number of possible values is infinite ...For the study described in Exercise 34, blinding will be used. What is blinding, and why was it important in this experiment? An x chart based on standard deviations (instead of ranges) is made by plotting sample means with a centerline at x and control limits at x + A3s and x A3s, where A3 is found in Table 14-2 and s is the mean of the sample ...
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