Questions and Answers
What should be done when a sample is deleted from a data set in the templates?
Leave the cells blank
What is the purpose of rescaling the vertical axis of the charts?
Both a and b
What is the common characteristic of the out-of-control samples in the x-bar chart?
They were all taken by the same operator
What should be done with the out-of-control samples in the x-bar and R-charts?
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What is the purpose of updating the number of samples used in the calculations when deleting sample data?
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What is the purpose of the new production data and revised control charts shown in the image?
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What is the purpose of constructing x-bar and R-Charts in process monitoring and control?
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Why is estimating process capability using control chart data less accurate than using the complete set of data?
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What should workers do after a process is determined to be in control?
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Why do workers need to be trained to use control charts properly in process monitoring?
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How are the overall mean and average range used in process capability index calculations?
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What is one limitation of using x-bar and R-Charts for estimating process capability?
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What modification should be made to the formula in cell C9?
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What should the formula in cell C10 be changed to?
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What is the reason for modifying the formulas in cells C9 and C10?
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What does changing the number of samples in cell E6 affect?
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Why should the formulas in cells C9 and C10 use only the column range of the original data?
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How does modifying the formulas in cells C9 and C10 affect the charting of data?
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What does the new ISO standard 11462-1 provide guidance for?
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What sample size is effective for detecting process shifts of two standard deviations or larger?
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What does the ISO standard 11462-1 address regarding SPC systems?
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In order to detect smaller shifts in the process mean, what range of sample size must be used?
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Where should the control limits be located according to the text?
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What aspect does the standard 11462-1 NOT provide guidance on?
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What is the purpose of a u-chart?
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What assumption is made when using a u-chart?
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Which statistic is used to compute the control limits for a u-chart?
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What is the first step in constructing a u-chart?
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What is the formula used to calculate the control limits for a u-chart?
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In the spreadsheet template example shown, what is the value of the lower control limit (LCL)?
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Control limits for x-bar and R-charts are the same as those for u-charts.
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Increasing variation in a process will lead to wider control limits in an x-bar chart.
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The ISO standard 11462-1 provides guidance on constructing individual charts.
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Low volume operations are best monitored using x-charts.
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An upward trend in the average values on an x-bar chart indicates a process improvement.
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Control limits for moving range-chart are calculated based on the average moving range.
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To estimate process capability using x-bar and R-charts, one should collect between 25 and 30 samples, with sample sizes generally between 3 and 10.
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The estimate of the standard deviation using control chart data is as accurate as calculating the standard deviation using the complete set of data.
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The overall mean and average range are used in process capability index calculations.
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To detect smaller shifts in the process mean, sample sizes between 3 and 10 should be used.
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After a process is determined to be in control, workers should continue using control charts to monitor performance and identify any special causes.
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The formula used to calculate control limits for a u-chart is provided in the text.
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The formula in cell C10 should be changed to calculate the upper control limit (UCL) for the u-chart.
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Updating the number of samples used in the calculations when deleting sample data is not necessary, as it does not affect the charting of the data.
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The ISO standard 11462-1 provides guidance on the aspect of defining the appropriate sample size for detecting process shifts of two standard deviations or larger.
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When a process is determined to be in control, workers should immediately start making changes to the process to improve its performance.
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The purpose of a u-chart is to monitor the number of nonconforming units in a sample, while an x-bar and R-chart is used to monitor the fraction of nonconforming units.
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The ISO standard 11462-1 provides guidance on the aspect of constructing and interpreting control charts for process monitoring and control.
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The formula in cell C9 should be changed to: =SUMIF(B13:AE13, ">-99999", B23:AE23)/$E$6.
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To maintain the established control limits, the number of samples in cell E6 should be increased when modifying the formulas in cells C9 and C10.
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Changing the formulas in cells C9 and C10 for the calculations of the grand average and average range will affect the established control limits.
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The template will no longer chart all the data once the modifications are made to cells C9 and C10.
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The modified formula in cell C10 should read: =SUMIF(B13:AE13, ">99999", B28:AE28)/$E$6.
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Cell E6 should be altered to reflect a different number of samples for more accurate calculations of the grand average and average range.
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The u-Chart for Nonconformances Per Unit Spreadsheet Template is designed for samples of equal size only.
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The formula to compute the average number of nonconformances per unit in a u-Chart is represented by the symbol 'u-bar'.
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The Control Chart Selection Control Chart Formula Summary provides guidelines on constructing x-bar and R-Charts.
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In the spreadsheet template example, the lower control limit (LCL) value is presented as 42.
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The ISO standard 11462-1 addresses specific limitations of using x-bar and R-Charts for estimating process capability.
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The purpose of updating the number of samples used in the calculations when deleting sample data is to maintain consistency in the dataset.
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