Overview for Acceptance Individuals Chart

Use an Acceptance Individuals Chart to detect when the out-of-specification percentage might exceed an acceptable level. Use when you have continuous data that are individual observations not in subgroups.

For example, a quality engineer monitors deviations from the target fill weight for a packaged product. The deviations are measured in tenths of an ounce. The engineer has determined that the process variation is stable. The upper specification limit is 26 tenths of an ounce above the target. The process is allowed to shift as long as no more than 1% of the output is expected to exceed the upper specification limit. The engineer measures 160 packages at appropriate time intervals and creates an Acceptance Individuals Chart.

Two observations are above the upper acceptance control limit. These points indicate that the process shifted far enough toward the upper specification limit that more than 1% of the process output might exceed the specification limit.

Note

The process variation must be in control before you assess the process center using an Acceptance Individuals chart because the acceptance control limits are calculated using an estimate of process variation. If the process variation is not in control, the acceptance control limits are not reliable and Minitab might produce a false out-of-control signal. Use a moving range chart to determine whether the process variation is in control.

Where to find this control chart

To create an Acceptance Individuals chart, choose Stat > Control Charts > Acceptance Charts > Individuals.

When to use an alternate control chart

If you can collect data in subgroups, use Acceptance Xbar Chart.