Certified Production & Operations Manager (POM) Practice Exam

What type of control chart would be recommended for tracking the number of late deliveries per day for a parcel delivery service?

1. p-chart

2. c-chart

3. R-chart

4. x-bar chart

The correct answer is: c-chart

The c-chart is recommended for tracking the number of late deliveries per day for a parcel delivery service because it is specifically designed to monitor counts of events that can occur over a fixed time period. In this case, the "events" are the late deliveries. The c-chart operates in scenarios where you are counting the number of occurrences of a certain characteristic (such as late deliveries) within a constant area of opportunity (like a day). It helps in identifying variations in the count of late deliveries over time, making it useful for quality control applications where you want to ensure the delivery service maintains a consistent performance. In contrast, other types of control charts serve different purposes. For instance, a p-chart is used for data that reflects the proportion of defective items in a sample, making it less suitable here. The R-chart is primarily for tracking the range within a subgroup, typically relating to variables data rather than count data. The x-bar chart focuses on the average values of a variable over different samples, which does not apply to counting occurrences like late deliveries. Thus, the selection of a c-chart aligns perfectly with the operational needs of tracking late deliveries in this context.