Causes of Different Out-of-Control Indicators As per control chart assignment help experts, there are three indicators in a control chart that single process is out-of-control due to some factor. The potential causes of different out-of-control indicators are discussed below along with examples.

Mean Level Drifting Upwards: A single point or observation is falling outside control limit (including USL and LSL) is the main cause of upward increase in mean level of control chart. For example, the following diagram shows that a single observation of population is located outside the upper control limit due to an error in computation of observation.

Sharp Change in Mean Level: The possible cause behind the sharp change in mean level is increasing or decreasing six data points on continuous basis or in the same row. Along with this, deteriorating maintenance and improvement in skill are also the potential reasons for this out-of-control indicator. At the same time, the out-of-control mean can also occur due to an operator error.  For example, a company product dials for a machine that has a constant diameter. The first 4 dials are selected on half-hour basis in 12 hours period that includes total 96 observations. In this case, if operator calculates wrong mean, it will change mean level of control chart. Along with these causes, following are some other potential causes of out-of-control signals.

• Two out of 3 points in a row more than 2? or below the center line.
• Variability increasing
• If patterns or trends are within the control limits

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