Data - Capability Analysis (Binomial)
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Use data from a binomial distribution. Each entry in the worksheet column should contain the number of defectives for a subgroup. When subgroup sizes are unequal, you must also enter a corresponding column of subgroup sizes.

Suppose you have collected data on the number of parts inspected and the number of parts that failed inspection. On any given data, both numbers may vary. Enter the number that failed inspection in one column. If the total number inspected varies, enter subgroup size in another column:

Missing Data

If an observation is missing, there is a gap in the P chart where the subgroup would have been plotted. The other plots and charts simply exclude the missing observation(s).

Unequal Subgroup Sizes

In the P chart, the control limits are a function of the subgroup size. In general, the control limits are further from the center line for smaller subgroups than they are for larger ones. When you do have unequal subgroup sizes, the plot of %defective versus sample size will permit you to verify that there is no relationship between the two. For example, if you tend to have a smaller %defective when more items are sampled, this could be caused by fatigued inspectors, which is a common problem. The subgroup size has no bearing on the other charts because they only display the %defective.