Simulation ISYE 6644 Midterm 1

Harry Markowitz (one of the big wheels in simulation language development) won his Nobel Prize for portfolio theory in 1990, though the work that earned him the award was conducted much earlier in the 1950s. Who won the 1990 Prize with him?

a. Merton Miller and William Sharpe

b. Henry Kissinger

c. Albert Einstein

d. Subrahmanyan Chandrasekhar

a

Which of the following situations might be good candidates to use simulation?

a. we put 5000 in savings account paying 2% continuously compounded interest per year, we are interested in determining account value in 5 yrs

b. investing one half of our portfolio in fixed-interest U.S. bonds and remaining half in stock market equity index, have some info concerning distribution of stock market returns, but don't really know what will happen in market

c. new strategy for baseball batting orders, would like to know if it beats commonly used batting orders, lots of randomness in baseball

b,c

Planet Glubnor has 50-day years, suppose there are 2 Glubnorians in the room. What's probability they will have same birthday?

1/50

The planet Glubnor has 50-day years.

Now suppose there are 3 Glubnorians in the room. (They're big, so the room is getting crowded.) What's the probability that at least two of them have the same birthday?

0.0592

Inscribe a circle in a unit square and toss n = 500 random darts at the square.

Suppose that 380 of those darts land in the circle. Using the technology developed in this lesson, what is the resulting estimate for pi?

3.04 (4*proportion in circle)

True or False Suppose X and Y have joint p.d.f. f(x,y) = cxy/(1+x^2+y^2) for 0

No, they are independent only if you can write f(x,y) with no funny limiys for some functions a(x) and b(y)

What is the most-important theorem in the universe?

Central Limit Theorem

Which steps are regarded as essential for a successful simulation study? (There may be more than one correct answer.)

a. problem formulation

b. model validation

c. model verification

d. experimental design

e. output analysis

a,b,c,d,e

Suppose that I have modelled the arriving calls to a call center as a Poisson process. What do I have to carry out in order to determine if that's indeed a reasonable model assumption?

model validation

which of the following times could be regarded as events?

a. customers arrive at justin's concert venue

b. justin forgets a lyric

c. justin sings wrong note

d. angry customers depart the venue

e. a customer is 11 years old

a,b,c,d

TRUE or FALSE? Customer waiting times are activities because these are typically explicitly specified in the simulation.

false

TRUE or FALSE? The simulation clock time is a variable.

true

TRUE or FALSE? The simulation clock time always equals real time.

false

TRUE or FALSE? In this class, time always moves forward.

true

TRUE or FALSE? A fixed-increment time-advance mechanism is used primarily in continuous-time models such as those involving differential equations.

true

TRUE or FALSE? A next-event time-advance mechanism is typically used in queueing models involving customer arrivals, services, and departures.

true

TRUE or FALSE? The future events list contains all known upcoming events, including arrival times, departure times, and machine breakdown times.

true

TRUE or FALSE? The FEL can be updated any time an event occurs.

true

TRUE or FALSE? It is possible for the system state to change between consecutive event times.

false

TRUE or FALSE? In a simulation using the "next-event" time-advance mechanism, the simulation clock moves to the most-imminent event.

true

TRUE or FALSE? When a new event occurs, the simulation may update the chronological order of the FEL's events by inserting new events, deleting events, moving them around, or even doing nothing.

true

TRUE or FALSE? Almost every discrete-event computer simulation language maintains a FEL somewhere. (Future Events List)

true

TRUE or FALSE? In Arena, you are responsible for maintaining the language’s FEL.

false

Which is generally the easier simulation modeling approach — Event-Scheduling or Process-Interaction?

a. event-scheduling

b. process-interaction

b

Which is the modeling approach adopted by Arena — Event-Scheduling or Process-Interaction?

a. event-scheduling

b. process-interaction

b

TRUE or FALSE? A simulation language incorporating the P-I approach considers the events that a generic customer undergoes as it passes through the system, and then automatically does the bookkeeping to keep track of how all such customers interact with each other.

true

How many simulation languages are there?

a. just a few

b. 5-10

c. 10-50

d. >>50

d

When selecting a simulation language, what characteristics do you have to take into consideration?

cost, ease of use, modeling world view, random variate generation capabilities, output analysis capabilities

What does Create do in Arena

Periodically generate customer arrivals

What does Process do in Arena

have work performed on the customers, maybe have to wait in line

What does Dispose do in Arena

Customers leave system after service

Create module in Arena

has fields for name of module, type of entity, interarrival distribution, # of customers per arrival, maximum # of arrivals allowed, time that the first guy shows up

Process module in Arena

has fields for name of module, type of action, service time

Dispose module in Arena

get rid of entities, can rename module

Delay action in Process module in Arena

spend time in the process (self-service)

seize-delay-release in Process module in arena

grab at least one resource (server), spend time getting served, and then free server for next customer

In arena if you seize and the server isn't available you may have to...

wait in a queue

Seize-Delay in Process module in Arena

grab at least one resource and spend time getting served

Delay-Release in Process module in Arena

use a previously seize'd server for a while, and then free him for the next guy to use

Schedule Spreadsheet

- can set schedules for servers

- can set schedules for arrivals

decide module in Arena, when an entity gets to a decide module, they can

- randomly go either of 2 locations

- go to any various locations

- go to either of 2 locations if a condition is satisfied

- go to any of various locations if condition is satisfied

decide module in Arena allows...

customers to make probabilistic and conditional choices about their paths

assign module in Arena allows...

to give values to attributes and variables, and even assign graphics to entities

how you can change attributes, variables and other things

Attribute spreadsheet

keeps track of existing attributes that can be defined in an assign, can make your own, and can be vectorized

variable spreadsheet does the same

entity spreadsheet allows you to set initial picture

We are interested in modeling the arrival and service process at the local McBurger Queen burger joint. Customers come in every once in a while, stand in line, eventually get served, and off they go. Generally speaking, what kind of model are we talking about here? (More than one answer below may be right.)

a. discrete

b. continuous

c. stochastic

d. deterministic

a, c

Who is William Gosset?

A) He invented the t distribution that is used ubiquitously in statistics.

YES or NO? Has anyone closely related to the field of computer simulation ever won a Nobel Prize?

Yes

Why might simulation be a good tool to analyze supply chains? (More than one answer below may be correct.)

supply chains often have complicated network structures, making exact analysis difficult

supply chains are stochastic systems, with random travel times, lead times, and order patterns

TRUE or FALSE? All random number generators perform pretty much the same.

false