Information Management Systems Test 3

In adjusted exponential smoothing, the closer beta is to ________, the stronger a trend is reflected.

1

Trends

A gradual, long-term, up-or-down movement of demand

Linear Trend

A linear regression model that relates demand to time

Correlation

A measure of the strength of the relationship between independent and dependent variables

Constant Service Times

A special case of the single-server model with undefined service times. There is no variability in service times; beta = 0. Typically used with machinery and automated equipment

Monte Carlo

A technique for selecting numbers randomly from a probability distribution. It is analogous to gambling devices.

Queuing System Operating Statistics

Are steady state, or constant, over time

L

Average number of customers in the queuing system (customers being serviced and in the waiting line)

Lq

Average number of customers in the waiting line

W

Average time a customer spends in the total queuing system (waiting and being served)

Wq

Average time a customer spends waiting in the queue to be served

Single-Server Model

Characterized by an infinite calling population, a first-come, first-served queue discipline, Poisson arrival rate and exponential service times.

________ is the percentage of the variation in the dependent variable that results from the independent variable.

Coefficient of determination

________ is a measure of the strength of the relationship between independent variable(s) and a dependent variable.

Correlation

The ________ is a procedure for developing a consensus forecast about what will occur in the future.

Delphi method

Linear Regression Methods

Develops a mathematical relationship between the forecasted item and factors that cause it to behave the way it does

________ is not part of a Monte Carlo simulation.

Finding an optimal solution

Times Series Methods

Forecasts are statistical techniques that use historical data

Delphi Method

Forecasts future using informed judgement and opinions from knowledgeable individuals

Characteristics of Moving Averages

Is good for stable demand with no pronounced behavioral patterns

________ indicates a forecast is biased high.

Large "-" Ebar

________ moving averages react more slowly to recent demand changes than do ________ moving averages.

Longer-period, shorter-period

________ is absolute error as a percentage of demand.

MAPD

MAD

Mean Absolute Deviation (MAD) is the average, absolute difference between the forecast and the demand. The lower the MAD, the more accurate.

MAPD

Mean absolute percent deviation (MAPD) is absolute error as a percentage of demand

Lambda

Mean arrival rate

Mu

Mean service rate

The ________ process is analogous to gambling devices.

Monte Carlo

________ is a technique for selecting numbers randomly from a probability distribution.

Monte Carlo

Random Numbers

Numbers equally likely to be chosen from a large population of numbers

U

Probability that the server is busy (probability that a customer has to wait) known as the utilization factor (U=lambda/mu)

I

Probability that the server is idle (probability that a customer can be served) I = 1-U or 1-(lambda/mu)

________ use management judgment, expertise, and opinion to make forecasts.

Qualitative methods

An important factor to consider in analyzing a queuing system is the:

Queue Discipline

Pseudorandom Numbers

Random numbers generated by a mathematical process instead of a physical process

Analogue Simulation

Replaces a physical system with an analogous physical system that is easier to manipulate

Manual Simulation

Simulation conducted by hand

Finite Queue

The length of the queue is limited

Infinite Queue

The length of the queue is unlimited

Queuing Discipline

The order in which waiting customers are served

Average Error

The per-period average of cumulative error

Coefficient of Determination

The percentage of the variation in the dependent variable that results from the independent variable

Characteristics of a Table of Random Numbers

The random numbers are derived from some artificial process, like a computer program. They are equally likely to occur.

Cumulative Error

The sum of the forecast errors

________ methods assume that what has occurred in the past will continue to occur in the future.

Time series

Why do we do simulations?

To help solve some real world problems. It provides a laboratory experimentation on a real system.

Multiple-Server Model

Two or more independent servers in parallel serve a single waiting line

Cyclical Patterns

Up-and-down repetitive movement in demand

Seasonal Patterns

Up-and-down, repetitive movement within a trend occurring periodically

Qualitative Methods

Use judgement, expertise, and opinion to make forecasts

Characteristics of Weighted Moving Averages

Weights are assigned to the most recent data

In a single-server queuing model, L represents the:

average number of customers waiting and being served.

A ________ is an up-and-down repetitive movement that repeats itself over a time span of more than 1 year.

cyclical pattern

Coefficient of determination is the percentage of the variation in the ________ variable that results from the ________ variable.

dependent, independent

A table of random numbers must be:

efficiently generated.

Which of the following will not decrease system utilization?

increase in arrival rate

In a finite queue, the length of the queue is:

limited.

Random numbers generated by a ________ process instead of a ________ process are pseudorandom numbers.

mathematical, physical

A limitation of simulation is that:

model building is costly and time-consuming.

A seed value is a(n):

number used to start a stream of random numbers.

Simulations are normally done:

on the computer.

Simulation does not usually provide recommended decisions. Instead it provides:

operating characteristics.

Developing the cumulative probability distribution helps to determine:

random number ranges.

The arrival rate is the:

rate of arrivals to the service facility.

In the Monte Carlo process, values for a random variable are generated by ________ a probability distribution.

sampling from

A ________ is a gradual, long-term, up-or-down movement of demand.

trend

Confidence Intervals

upper confidence: Xbar + (1.96)(s/sqrt[n]) lower confidence: Xbar - (1.96)(s/sqrt[n]) xbar is the mean and s is the sample SD from sample size n