Deck 22: Simulation

Question 1

Spreadsheets are extremely strong in their ability to conduct dynamic simulation analysis.

Answer 1

False

Question 2

____ trace the detailed logic or actions that occur in the system in a step-by-step fashion over time.

A)Validations
B)Verifications
C)System simulation models
D)Entities

Answer 2

C

Question 3

All of the following are disadvantages of simulation except

A)Limited application
B)Difficulty of collecting the appropriate input data
C)Selecting the correct probability distribution
D)The accuracy of outputs

Answer 3

A

Question 4

Using two-digit random numbers, the interval 55 - 79 represents what probability?

A)0.55 to 0.79
B)0.25
C)0.24
D)0.67

Question 5

'Face validity' means the programmers agree to the model's logic.

Question 6

Which of the following is not correct regarding next-event simulation models?

A)Used more commonly in practice
B)Basis for most commercial simulation software
C)Waste computer time
D)More accurate than fixed-time-increment simulation

Question 7

A simulator is a general purpose simulation model.

Question 8

There is no single test to prove that a model is 100% valid.

Question 9

The Excel function (RAND ) generates random numbers that provide a continuous range of values. Unlike those for two-digit numbers, these values are not limited to probability increments of 0.01.

Question 10

Face validity involves asking people familiar with the real system to evaluate the assumptions and logic of a model.

Question 11

It doesn't make sense to use simulation for waiting-line problems since queuing models give optimal solutions.

Question 12

'Balking' means a customer finds the wait while in line too long and thus leaves the line.

Question 13

If variability of demand were the only source of uncertainty, the order quantity and reorder-point decision could be based on a single-period inventory model.

Question 14

Which is correct regarding a simulation model for inventory management?

A)Only demand can vary
B)The goal is to minimize waiting time
C)Looks at a combination of order quantity and reorder point
D)Does not allow backorders of stockouts

Question 15

Which of the following is not an advantage of simulation?

A)Convenient experimental laboratory
B)Can perform 'what-if' studies
C)Don't have to disturb current process
D)Yields optimal solution

Question 16

A disadvantage of simulation models is that the structuring is highly dependent on the expertise of the modeler.

Question 17

Needing the actual time of arrival and actual time of serving relates best with

A)Fixed-time-incremental simulation
B)Next-event simulation
C)Random numbers
D)Queuing formula

Question 18

With a fixed-time-increment simulation model, detailed information is lost.

Question 19

The queuing model operating characteristics formula only characterizes short-term average results and, in many practical situations, managers are interested in understanding long-term dynamic behaviors of queuing systems

Question 20

In general, as the number of probabilistic components of a system increases, the more likely it is that simulation will be the best analysis approach.

Question 21

A busy municipal golf driving range prepares 300 hotdogs daily. For a variety of reasons, the daily demand for hotdogs varies as follows:
$$\begin{array} { c c } \underline{\text { Demand Units} } & \underline{\text { Probability }} \\150 & 0.15 \\200 & 0.20 \\250 & 0.60 \\300 & 0.05\end{array}$$
a. If the hotdogs sell for $1.50 each and cost $0.80 each, determine the range's profit or loss on hotdogs for day three using the following random numbers: 00, 59, 02, 97, 69, 98, 93, 49, 51, 92.
b. If the hotdogs sell for $1.50 each and cost $0.80 each, determine the range's profit or loss on hotdogs for day eight using the following random numbers: 00, 59, 02, 97, 69, 98, 93, 49, 51, 92.
c. If the hotdogs sell for $1.50 each and cost $0.80 each, determine the average daily demand for hotdogs using the following random numbers: 00, 59, 02, 97, 69, 98, 93, 49, 51, 92.

Question 22

All of the following are verification techniques except

A)Developing logical flow charts
B)Testing the probability distribution used to drive the simulation and behavior of system entities
C)Breaking the problem into smaller pieces or modules
D)Codes can be checked by others, not just the programmer

Question 23

Larry sells sweatshirts at football games. The quantity supplied to him is sometimes less than he ordered. The probability distribution below shows the probability of these shortages.
$$\begin{array} { c c } \underline{\text { Sweatshirts units shart) }} & \underline{\text { Probability }} \\0 & 0.5 \\100 & 0.3 \\200 & 0.2\end{array}$$
Simulate the average number of shortages for 15 consecutive orders, using the following single digit random numbers: 1, 6, 8, 3, 4, 5, 7, 0, 3, 8, 9, 3, 2, 4, 2.

Question 24

Explain the major differences between a fixed-time and a next-event simulation model. Include advantages and disadvantages of each.

Question 25

A local legal aid office provides basic legal assistance to walk?in clients. The historical arrival frequency is as shown below:
$$\begin{array} { c c } \text { Clients Arriving } & \text { Relative } \\ \underline { \text { Per Hour } } & \underline { \text { Frequency}} \\ 1 & 20 \% \\ 2 & 30 \% \\ 3 & 40 \% \\4 & 10 \% \\\end{array}$$

Service times are characterized by a normal distribution with a mean of 10 minutes and a standard deviation of 4 minutes. They are interested in using simulation to find the total amount of service time for each hour of a six-hour working day. They generated the following random numbers for hours 1?6 respectively: 63, 13, 67, 50, 71, and 25.
a. On a scale of 00?99, what random number range corresponds to 3 clients arriving per hour?
b. What is the number of clients arriving in hour 4?
c. What is the total service time in minutes for hour 1?

Question 26

A lumber company sells 8?foot 2x4's to construction companies in three states. They have historical sales demand in thousands) for the past 26 weeks, as shown below:
$\begin{array}{ccc}\text { Historical } & \text { Number of } & \text { Relative }\\\underline{\text { Sales } \$ 000 )} &\underline{\text {Weeks Sold }} &\underline{\text { Frequency }}\\5-10 & 5 & .19 \\11-20 & 7 & .27 \\21-30 & 8 & .31 \\31-40 & 6 & 23\end{array}$
They are interested in determining the average number of sales per category for the next five weeks using simulation. They generated the following random numbers for weeks 1?5 respectively: 63, 13, 67, 50, and 71.
a. Based on a scale of 0-99, what random number range should be allocated to sales category of 11-20?
b. What is the average sales corresponding to week 2?
c. What is the average sales over all five weeks?

Question 27

A computer implementation free from logical errors and bugs refers to

A)Verification
B)Validation
C)Simulation
D)ProcessModel

Question 28

Validation consists of all of the following except

A)Developing a model with high face validity
B)Validating model assumptions
C)Developing logical flow charts
D)Validating model output

Question 29

Define simulation and give some operations management examples.

Question 30

The table below shows the frequency of service times for a drive-through window.
$$\begin{array} { c c } \underline{\text { Service Time minutes)} } & \underline{\text { Frequency }} \\1 & 2 \\2 & 6 \\3 & 8 \\4 & 13 \\5 & 13 \\6 & 7 \\7 & 1\end{array}$$
a. If the first category service time of (1 minute) started with random number 00, determine the random numbers for a service time for Category 5, five minutes.
b. Determine the random numbers for a service time of seven minutes if the first category starts at random number 00.

Question 31

The Rose Warehouse buys roses each week from Panama. A toll?free long distance call is made on Saturday night, and early Monday morning roses arrive at the airport in a box refrigerated with dry ice. The roses cost $8 a dozen and are sold on a cash-and-carry basis for $28 a dozen. Roses left over at the end of the week are put in a trash collector in an alley behind the store. Past sales rounded to the nearest ten dozen) are as follows:
$\begin{array}{cc}\text { Dozens of Roses } & \text { Relative } \\\underline{\text { Demanded }} &\underline{ \text { Frequency }}\\110 & 5 \\120 & 20 \\130 & 25 \\140 & 30 \\150 & 20\end{array}$

The owner of the Rose Warehouse wants to compare two ordering rules for ordering roses: 1) order last week's demand plus 10 dozen extra as (safety stock), (2) order 130 dozen every week. He wants to run an eight-week simulation to compare the average weekly profit for the two rules. Last week's demand was for 110 dozen. He generated the following random numbers for weeks 1?8, respectively: 63, 13, 67, 50, 71, 25, 44, and 00.
a. What is the random number range corresponding to 130 dozen roses demanded?
b. Using ordering rule 1, what is the profit for week 3?
c. Using ordering rule 2, what is the profit for week 6?
d. What is the average profit over all eight weeks for ordering rule 1?

Question 32

Under what situation would an analytical queuing model be used? When would a simulation model be used?

Question 33

Discuss three advantages and three disadvantages of simulation models.

Question 34

In regard to a simulation model for inventory management, all of the following are correct except

A)Results in an optimal solution with a large simulation
B)Many days of simulation run are needed to obtain meaningful results
C)Lead-time can vary
D)Assumes that a specific reorder point and order quantity have been selected

Question 35

Simulation language ProcessModel contains all of the following except

A)Objects
B)Connections
C)Action logic
D)Simulators

Question 36

Differentiate and explain the importance of verification and validation.

Question 37

Discuss a simulator. How does it differ from simulation software such as ProcessModel?

Question 38

A pastry store wants to know how many dozen muffins to bake each day. Every dozen they sell fresh in the shop returns a profit of $5.00. Every dozen they bake but do not sell on the day they are baked is given to a local charity at a loss of $3.00 a dozen. The business is fairly stable in that they never sell less than 50 dozen nor more than 80 dozen muffins. Their sales history, rounded to the nearest ten dozen muffins is as shown:
$$\begin{array} { c c } \text { Dozens of } & \text { Number of Days } \\ \underline{\text { Muffins Sold }} & \underline{\text { That Mary Sold} } \\ 50 & 12 \\60 & 37 \\70 & 45 \\80 & 18\end{array}$$ They want to run a ten day simulation for production rates of 50, 60, 70, and 80 muffins to determine the profit loss) for each. They generated the following random numbers for days 1?10 respectively: 63, 13, 67, 50, 71, 25, 44, 00, 56, and 68.
a. What range of random numbers corresponds to 70 muffins sold?
b. What is the profit for day 3 if they make 70 dozen muffins?
c. What is the average daily profit for all ten days) corresponding to 60 dozen muffins made?

Question 39

Given the table below with information on lead-time, followed by a set of six random numbers, determine the average lead-time.
$$\begin{array} { c c } \underline{\text { Lead The days) }} & \underline{text { Frequency }} \\ 3 & 20 \% \\4 & 70 \% \\5 & 10 \%\end{array}$$
RANDOM NUMBERS: 90, 52, 54, 47, 56, 95