Data - P Chart Diagnostic, P Chart, and Laney P' Chart
main topics 

You must have at least one column that contains the number of defectives. Each row of a column should contain the number of defectives for one subgroup.

If the subgroup sizes are different, you must also include a column that indicates the size of each subgroup. If the size is the same for each subgroup, you can enter the subgroup size directly in the dialog box instead of providing a column.

Suppose that, at a manufacturing plant, you collect data each day on the number of parts that failed inspection. The number of defectives is the number of parts that failed on a given day. The subgroup size is the number of parts that you inspected that day. Your data might look like the table below.

Each row in the table represents a single day. The Failed column indicates the number of defectives for the day. The Inspected column indicates the number of parts inspected that day.

The P Chart and Laney P' Chart divide the number of defectives by the subgroup size to calculate the proportion of defectives for each subgroup.

The control limits for the P Chart and Laney P' Chart change depending on the size of each subgroup. In general, the control limits are further from the center line for smaller subgroups than they are for larger ones. You can force the control limits to be constant by entering a fixed subgroup size, for example the average subgroup size. See To force control limits and center line to be constant.

When an observation is missing, a gap exists in the chart for that observation.