The funny thing about “the average customer” is that no such person exists. No matter how much you learn about this fantastical creature, you still know nothing about any particular person who comes into your store. If some of your customers are spending a lot of time setting up registries, others are making exchanges, and still others are just browsing, the “average customer” might be staying for 20 minutes, while all of the actual customers fall above or below that number.

So how do you deal with the variation in flow that results from customers looking for different experiences? Of course, there’s no substitute for actually getting to know them as individuals. But operations management does have some devices for dealing with complex flow structures that will get your analysis a little closer to the reality on the ground.

We start by dividing the customers into types, according to the different paths they take through the system. It helps to visualize a complex situation like this with a process flow diagram. In the diagram below, three different possible paths through a system are indicated with color-coded arrows. (We could easily add other paths, but for this introduction we’ll keep it very simple.) Each rectangle represents a different resource, and as you can see, not every resource necessarily serves every customer. (Flow units are represented by triangles.)

Next week, we’ll show you how to calculate the exact utilization for each of the resources, and how to adjust for different processing times for different kinds of customer.