Final answer:
Service variability refers to the inconsistencies in service quality that can occur due to various factors. It is not influenced by the time since the last customer was served, which is described by the memoryless property.
Step-by-step explanation:
Service variability means that the quality and consistency of a service can vary greatly depending on a wide range of factors such as who provides the service, when and where it is provided, and to whom. In the context of customer service distribution, one might assume that the time spent waiting for the next customer would depend on the time since the last customer was served. However, this is not the case. The likelihood of a customer arriving is not influenced by how long it has already been since the last customer was served. This phenomenon is described by the memoryless property, which states that the probability of a future event (like a customer arrival) is not affected by the elapsed time since a past event (the last customer).