Industrial Statistics with Minitab

15.2 Capability Study for Variables that Follow a Binomial Distribution

The number of unsatisfied customers in file BANK.MTW is a typical example of a variable that follows a binomial distribution. It must be assumed that all of the agencies have the same instructions, the same products, and that they all follow the same procedures in their relationships with their customers. The question of interest is to find out which is the percentage of unsatisfied customers that are produced by these products and the standard procedures of the bank.

Stat > Quality Tools > Capability Analysis > Binomial

Output in the session window:

Graphical window:

1. Control chart for the proportion of unsatisfied customers. We observe the points outside control as pointed out in the Session window.

2. Cumulative proportion of defects. It must stabilize around the mean value to make sure that the number of samples is representative.

3. Representation of the values in binomial probability paper. We observe three points far away from the line.

4. Histogram of the ‘defects’ together with a reference line that is located on the target value which, in this case, is the default value: 0.

5. Summary statistics: ...