了解如何提升工作效率和提高质量标准，学会分析和改善服务业或制造业商务流程。主要概念包括流程分析、瓶颈、流程速率和库存量等。成功完成本课程后，您可以运用所学技能处理现实商务挑战，这也是沃顿商学院商务基础专项课程的组成部分。
响应力单元班次 1 视频课程
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运营管理概论（中文版）
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第 4 单元 - 质量
质量并不是运营管理唯一的重点，但是质量对于企业长期发展和成功至关重要。本模块将介绍运营中与质量的几个主要方面，导致缺陷的常见原因、发现质量问题以及保障可靠性和标准的常用实践方法。本模块教学结束后，您将了解缺陷可能发生的原因，并且能针对质量和稳定性提出合理的方法。
Rencontrer les enseignants
Christian TerwieschAndrew M. Heller Professor at the Wharton School, Senior Fellow Leonard Davis Institute for Health Economics Co-Director, Mack Institute of Innovation Management
The Wharton School
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,
Twelve customers over the hour, and the average processing time has remained at
four minutes. Yet, despite its utilization of 80%,, you
see that the picture changes dramatically. I noticed that some patients, if you
consider the patient number five and six here, these poor folks have to wait three
or four times as long as their actual service times.
Instead of looking at the patient wait times and service times, I can also look
at the inventory. And you see that at certain moments and
times, I might have three, if not four, patients in the practice.
All of that at the utilization of 80%.. When a doctor has six patients per hour
arriving to her waiting room, and the doctor can only see three patients per
hour, the times the patients will have to wait get longer and longer.
This is clearly a result of insufficient capacity.
Whenever you encounter waiting problems, the first thing that you should think
about is what can I do to inccrease the capacity of the resource? What we've done
in our earlier discussion in the module on productivity analysis, is a really good
toolbox to free up some capacity. We also talked about flexibility, and
making sure that we have the capacity available at the right time.
However, we notice in this session, that oftentimes waiting is not just driven by
insufficient capacity, but it's driven by variability.
We notice that variability doesn't average itself out.
Think about it. Would you jump into the lake, headfirst,
if the lake is deep ten feet on average? Averages really only tell half of the
story. For this reason, in this module, we'll
focus a lot on variability, which is an important way to describe both the demand
process and the supply process beyond the simple averages.
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