Do you know what I find is the biggest pain when you get sick?

It's not the pain in your teeth, in your ear, or wherever you have your medical

complications. The biggest pain is a pain of waiting.

You call the doctor's office, they put you on hold for ten minutes.

You want an appointment for this afternoon, you get one for next week.

You finally arrive to your appointment, which is at two:00, you sit in the waiting

room, and there it is, four:00. Medical care, just like many other

services, is all about waiting, waiting, and waiting.

But why do customers have to wait? Why can't the care not be instantaneous?

In this module, we want to understand the concept of responsiveness.

How can we be quick in responding to our customers?

Waiting, of course, is just another form of mismatch between supply and demand.

When we are waiting, we as patients in the waiting room, are inventory.

And it's simply no fun being inventory, when your ear is infected or your teeth

hurt. So, understanding the match between supply

and demand once again, is going to be a crucial issue of solving this waiting time

problem. Now, let's represent a physician office in

form of process flow diagram. This is a really simple process flow

diagram. We have a waiting room and we have the doc

doing the work as the only resource in the system.

Let's say, for sake of arguments, that patients arrive at a rate of every five

minutes. So, over the course of an hour, we have

twelve patients come in per hour. Moreover, let's assume the doctor spends

an average ten minutes to serve a patient. That means we have a capacity of six

patients per hour. But first, let's ask ourself, what's the

implied utilization in the system? Now, remember from our discussion of

process analysis, that the implied utilization looks at the ratio between

demand and capacity, Which, in this case, is simply twelve

divided six equal to 200%.. How long will patients have to wait in

this practice? To see how long patients have to wait,

let's just do the following thought experiment.

Let's just look at the day in the life of the doctor and start early morning, say at

eight:00 a.m. when the practice opens. The first patient who comes into the

practice, probably, will not have to wait, and gets served immediately.

However, as the day unfolds, things get worse.

Of course, we have twelve patients per hour come into the practice, and six

patients per hour being served. What happens is we have an accumulation of

waiting patients. Inventory.

How quickly does this accumulation occur? Well, here we have twelve patients come

in, We have six patients get served.

So, every hour, we're accumulating six patients in the waiting room.

For example, at ten:00 a.m., I have twelve patients in the waiting

room. At noon, I've been operating for four

hours at a capacity short fall of six, and I will have 24 patients in the waiting

room. So, the person who comes in here at noon

has 24 patients in front of him or her. Every one of them will take ten minutes

and so the waiting time will be a total of 240 minutes.

Quite a long time, a pretty scary example. Let's look at another example.

Here is another doctor's office. Same thing, same process flow diagram, and

a patient arriving every five minutes. So, twelve patients arriving per hour.

It takes this doctor here, however, only four minutes to serve the patient.

So, a capacity is much higher, and the doctor can have a capacity of fifteen

patients per hour. We can compute the utilization now as the

ratio between the flow rate to capacity and the flow rate, remember, is a minimum

of demand and capacity. And so, the flow rate is twelve, the

capacity is fifteen, and we have a utilization of 80%..

Surely, in this practice, no patient will ever have to wait or maybe, they have to.

Imagine this doctor would be called Dr. Toyota Now, Dr.

Toyota runs a very proper practice. His patients arrive exactly every five

minutes. So, one at seven:00,00, one at seven:05,05

seven:10, and so on. Moreover, Dr.

Toyota knows what he is doing. He has standardized his work to a

four-minute processing time. The patient is still half undressed, after

four minutes Dr. Toyota says, sorry got to go, business is

business. Well, this is arguably a very unrealistic

example. I make things realistic in just a moment,

but I want you to see a very important point.

It is indeed possible to run a business with a utilization of 80%.

And have no waiting at all. Look how the patients arrive and when they

leave. Four minutes of work, a minute of idle

time for Dr. Toyota, four minutes of work, a minute of

idle time and none of these patients ever will have to work, wait.

Now arguably, my story of Dr. Toyota was very unrealistic.

What type of doctor would serve exactly every patient in four minutes?

What type of patients would arrive and get sick exactly one patient every five

minutes? Now, what do we mean with unrealistic?

More realistically, we would say that the arrival times when these patients come to

the practice are somewhat random. I will formalize the idea of randomness in

just a moment, but consider the example here of twelve patients spread out over 60

minutes in less of an assembly line fashion.

Moreover, look at the processing times for these twelve patients, some of them are

longer, Others is shorter.

This, I think what most of us would mean with a more realistic set of processing

times and the arrival times. Now, look what happens in this more

realistic setting. Notice, first of all, that our utilization

has still remained at 80%. Because after all, the average time

between two customers' arrivals is one customer every five minutes,