Zoila Gonzalez
MODULE TWO: MEASURING PROCESS FLOW
Instructions
1. Read the scenario presented and answer the related questions.
2. Submit your work as a pdf through the appropriate link in Blackboard.
Scenario 1: World’s Largest McDonalds
You are driving from Dallas to St Louis and you stop at the world’s largest McDonalds. (At least
the sign claimed it was the largest.) The average number of people waiting in line during lunch hour
is 30. During this period 5 people per minute leave the restaurant after receiving service.
On average, how long do customers spend waiting in line?
Solution
The verage number of people waiting (WIP) = 30
People who leave the restaurant after receiving service per minute (Throughput) = 5
Applying the Little’s Law formula:
CT = WIP/ λ
CT = 30/5 = 6 minutes.
On average, customers spend 6 minutes in line waiting.
Scenario 2: Hopkins Credit Union
Draft accounts at the Hopkins Credit Union carry an average balance of $8,000. The Credit Union
turns over its balance 6 times per year.
On average, how many dollars flow through the Credit Union (per account) each month?
Solution
Average balance = 8000
Turns over = 6 times
Dollars flow (year) = 8000 * 6 = 48000
Dollars flow (month) = 48000/12 = 4000
On average, it flows $4,000 through the Credit Union each month.
Problem Sets 2022 Page 1 of 4
Zoila Gonzalez
Scenario 3: Pediatric ED
The Pediatric ED is currently organized so that all patients register through an initial check-in
process. At his or her turn, each patient is seen by a doctor and then exits the process, either with a
prescription or with admission to the hospital. Currently, 25 people per hour arrive at the ED, 20%
of whom are ultimately admitted to the hospital. On average 2 people are waiting to be registered
and 30 are registered and waiting to see a doctor. The registration process takes, 4 minutes per
patient. Among patients who receive prescriptions average time spent with a doctor is 10 minutes.
Among those admitted to the hospital, average time is 30 minutes. Assume that the process is stable,
meaning that average inflow rate equals average outflow rate.
Data
Avg. of people who arrive at the ED per hour = 25
Avg. of people waiting to be registered per hour = 2
Avg. of registered people but waiting to see a doctor = 30
Avg. registration process per patient = 4 minutes
Avg. time spent with a doctor for patients who receive prescriptions = 10 minutes
Avg. time spent with a doctor for patients who are admitted to the Hospital = 30 minutes
Avg. inflow = Avg. outflow = 25 people per hour.
Avg. of people admitted at the Hospital per hour = 20% = 5
Avg. of people with prescription per hour = 80% = 20
Process
Computing
Avg. Patients
Throughput (patients/ hour)
Flow time (min)
Buffer 1
Waiting for
registration
2
25
4.8
Registration
1.67
25
4
Buffer 2
Waiting for a
Doctor
30
25
72
Doctor
Patients Patients Prescription
Admission
3.33
2.5
20
5
10
30
Buffer 1
a = 0.08 = 4.8 min
Registration
b =25*4/60 = 1.67 pat
Buffer 2
c=30/25=1.2hrs=72 min
Doctor
Patients - Prescription
d=20*10/60=3.3 pat
Patients - Admission
e=5*30/60=2.5 pat
Problem Sets 2022 Page 2 of 4
Zoila Gonzalez
On average, how long does a patient spend in the ED when all steps including waiting times are
included? (Note: those admitted and those not admitted have slightly different flows and average
times are a weighted average of these two values.)
Solution
Flow time
Minutes
Patients - Prescription
Patients - Admission
= 4.8 + 4 + 72 + 10
= 4.8 + 4 + 72 + 30
Avg. patient spend in the ED
Weighted average
= 80%*90.8 + 20%*110.8
90.8
110.8
94.8
On average, a patient spend in the ED when all steps including waiting times are
included is 94.8 minutes.
On average, how many patients are being examined by Doctors? (Note: There will routinely
be more than 1 doctor working in the ED. This value does not include time waiting to see the
doctor.
Doctor
Patients - Prescription
d=20*10/60=3.3 pat
Patients - Admission
e=5*30/60=2.5 pat
Total patients = 3.3 + 2.5 = 5.8
On average, the number of patients are being examined by a doctor is 5.8.
On average how many patients are in the ED including those waiting and those being
processed?
•
•
•
•
Patients waiting for registration= 2
Patients registered = 1.67
Patients waiting for a doctor = 30
Patients seeing doctor = 5.8
Total Patients
= 2 + 1.67 + 30 + 5.8
39.5
On average, the total number of patients in the ED is 39.5.
Problem Sets 2022 Page 3 of 4
Zoila Gonzalez
Scenario 4: The OuchGoWay Hernia Clinic
The OuchGoWay Canadian Hernia Clinic is a single condition medical facility that performs
hernia surgeries. Some surgeries are for single hernias and others are for double hernias. (If you
don’t know what a hernia is, consider yourself lucky.) On average one third of the patients
checking in each day have double hernias. These patients generally stay for 2.6 nights – twice as
long as the average patient with a single hernia.
1. On an average day 25 patients check in. On average, how many patients of each type are
in the clinic on a given day?
Avg. Patients check in = 25
Double hernia ratio = 1/3
Avg. Patients double hernia = 25*1/3 = 8.33
Avg. Double hernia nights = 2.6
I=R*T = 8.33*2.6 = 21.66 double hernia patients
Single hernia ratio = 2/3
Avg. Patients single hernia = 25*2/3 = 16.67
Avg. Single hernia nights = 1.3
I=R*T = 16.67*1.3 = 21.67 single hernia patients
2. How many times per month does the clinic turn over its inventory of patients (assume it
operates 7 days per week and has 30 days in a month).
Total patients = double hernia patients + single hernia patients = 21.66 + 21.67 = 43.33
Avg. Patients check in = 25
Turns over = Avg. Patients check in/ Total patients = 25/43.33 = 0.58 turns per day
Turns per month = 0.58 * 30 = 17.4
3. The cost of the actual procedure is fully covered by the Government, but the patient pays
for the room. The average double hernia patient pays a rate of $250 per day and single
hernia patients pay an average of $210 per day. What is the average revenue the clinic
receives per day per occupied room?
Avg. double hernia patient rate = $250 , Avg. single hernia patient rate = $210
Total patients = 43.33, Single hernia pat = 21.67 (50%), Double hernia pat = 21.66 (50%)
Answer:
Avg. revenue the clinic receives per day per occupied room =
Dou. hernia pat. rate*50% + Sin. hernia pat. rate*50% = $250*50% + $210*50% = $230
Problem Sets 2022 Page 4 of 4