Types of Control Charts

ProDiver control charts fall into one of two categories: variable or attribute.

  • Variable control charts plot measurable process data in a time-ordered sequence.
  • Attribute control charts plot data that is counted instead of being measured.

You can use ProDiver to produce the following types of control charts:

X-Charts present variable data. Each data point is the statistical mean of a subgroup of values.

The statistical principles used in calculating the UCL and LCL are based on normal distribution. By default, UCL and LCL are calculated at three standard deviations from the mean. However, these values can be adjusted on the Graph Options dialog box, Statistics tab.

P-Charts are used for data that is counted. Each data point is a ratio of its own discrete sample set. P-Charts can display fraction nonconforming or percent nonconforming data values.

The statistical principles used in calculating the UCL and LCL are based on binomial distribution.

NP-Charts are used to present the number of nonconforming or conforming items. The sample subgroup size must be uniform.

The statistical principles used in calculating the UCL and LCL are based on binomial distribution.

C-Charts display the number of nonconforming or conforming items within a consistent unit size, or the probability of a specific number of occurrences in a specific period of time.

The statistical principles used in calculating the UCL and LCL are based on the Poisson distribution.

U charts display the average count of nonconforming items per unit when the unit size is variable.

The statistical principles used in calculating the UCL and LCL are based on the Poisson distribution.

MR charts display the moving range over time to monitor process variation for individual observations.

The UCL and LCL are based on the moving range between observations.

Individual MR charts display individual observations and moving ranges over time for variable data.

The UCL and LCL are based on the moving range between observations.

You can create a custom data control chart for which you must manually enter a control data column, UCL, CL, and LCL.

 

See also Control Chart Formulas.