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Module
2: Time Series Decomposition
Defines
and illustrates the basic terms of time series forecasting:
time plots, trends, seasonality, cyclical factors, special events
and noise. Participant learns how to tell global from local
trends, how to distinguish types of seasonality, how to calculate
seasonal indexes and use them to deseasonalize data, and how
to avoid extrapolating noise.
-
The principle of decomposition
- Assessing
trends
- Seasonal
indexes and seasonal adjustment
- Leading
indicators of the business cycle
- Tracking
special events
- Recognizing
noise in the data
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Module 3: Forecasting Accuracy
The
many do's and don'ts in measuring forecasting accuracy. The
participant learns that measures of goodness of fit are not
a reliable guide to forecasting accuracy, learns how to set
up out-of-sample tests of forecasting accuracy and how to interpret
statistical measures of forecast accuracy.
- Goodness
of fit vs. forecast accuracy: Fit
to the past is a risky guide to forecasting performance
- Within-sample
vs. out-of-sample tests
- Rolling
out of sample evaluations: A
highly efficient procedure for assessing forecasting accuracy
- 3 Principle
statistical measures of forecast accuracy: MAD, MAPE, and
RAE
- Experiential
vs. theoretical prediction intervals: which to trust?
- Designing
an out-of-sample test: How much
data to hold out, and how many test periods to use
- Forecasting
competitions: M-Comp to the M3-Comp
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Module 4: Introduction to Exponential Smoothing
Exponential
smoothing is today the most widely practiced method of extrapolative
forecasting. The participants learn how it works, why it is
so versatile, whether automatic implementation of these models
can be trusted, and how to deal with problem data.
- Why smoothing
is so widely applied
- The family
of smoothing model
- Weighting
the data: weighting gives more
emphasis to the recent than to the distant past
- Modes
of implementation: manual, standard and automatic
- Choosing
a smoothing model
- The big
three: Simple, Holt and Winters' smoothing models
- Understanding
and explaining the forecasts
- Damped
and exponential trends
- Automatic
model selection
- Dealing
with intermittent series - Croston's approach
- Strengths
and weaknesses of exponential smoothing
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Module 5: Modeling Special Events
Many
time series have been jolted by special events. Unless these
are recognized and adjusted for, the forecasts may go awry.
In this module, the participants learn how to recognize, code
and account for special events.
- Types
of special events: disruptions, holidays, promotions
- Consequences
of ignoring a special event
- Identifying
the timing of a special event
- Special-event
adjustments to exponential smoothing models
- Event
index: measuring the effect of a special event
- Multiple
events and event interactions
- Using
event adjustments to represent explanatory variables
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Module 6: Forecasting for Product Hierarchies
Organizations
frequently must forecast at different levels - company wide,
by product or brand, and by item produced (sku). Multilevel
(or hierarchical) forecasts must be made to reconcile. In this
module, the participant sees many examples of product hierarchies,
compares three major approaches to reconciliation - top down,
bottom up and middle out - and learns how to make effective
use of group level data to forecast individual sku's.
- Hierarchical
forecasts and need for reconciliation
- SKU (stock-keeping
unit) data: often nasty, brutish
and short
- Three
reconciliation strategies: bottom-up, top down and middle
out
- Multilevel
exponential smoothing
- Using
good group data to forecast
poor item data
- Special
event adjustments in a product hierarchy
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Module 7: Refresher on Statistical Testing
Over
time, we tend to forget the logic behind and meaning of statistical
significance tests; but these make an important contribution
to the selection and evaluation of forecasting models. This
brief module covers the essence - skipping technical details
- of statistical testing, preparing the participant for the
application of statistical test in ARIMA and Regression.
- Testing
for Statistical Significance
- The Prob.
Value
- The "t"
ratio and "t" test
- Meaning
of statistically significant differences
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Module
8: Overview of Box - Jenkins Models (Arima)
Box
and Jenkins models try to improve upon the method of exponential
smoothing by considering a new information source. Called autocorrelation,
and representing the tendency that series "in motion tend
to remain in motion", its measurement opens the doors to
a method that can be very useful for data that lack strong trends
and seasonal components. This module is an overview, illustration
the potential benefits of the Box-Jenkins approach as wll as
the difficulties in its implementation and interpretation.
- What
does ARIMA stand for?
- How does
ARIMA differ from Exponential Smoothing?
- Creating
lagged variables
- Autocorrelations:
the key to understanding ARIMA
- Types
of ARIMA models:
- Autoregressive
Models
- Moving
Average Models
- Mixed
Models
- Three
step approach to model building:
- Identification
- Estimation
- Validation
- Explaining
the forecasts
- Series
1. ARIMA at its best. Smoothing at its worst
- Series
2. ARIMA and Smoothing: Too close to call
- Series
3. ARIMA breaks down for short time series
- Strengths
and weaknesses of ARIMA
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Module 9: ARIMA Modeling
For
those wishing to extend their knowledge of ARIMA to be able
to make custom model identifications, more comprehensive validations
and to better understand how ARIMA forecasts are made. This
module relies heavily on graphical tools but introduces a limited
amount of algebra.
- Autoregressive
(AR) and Moving Average (MA) Terms
- Autocorrelations
and Partial Autocorrelations
- Model
Identification
- Non-stationary
processes and differencing
- Automatic
Model Identification
- Model
Validation
- Deriving
the forecasts
- ARIMA
equivalents to Exponential Smoothing
- Extensions
of ARIMA
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Module 10: Regression Models for Forecasting
Regression
is the basic tool for measuring the relationship between variables.
If developed carefully, a regression model can also be a useful
forecasting tool, but cannot be readily automated in the manner
of extrapolative forecasting procedures. In this module, the
participant will learn what a regression model attempts to accomplish,
the challenges it must overcome, some procedures for determining
elasticities, seasonal effects, and delayed impacts of explanatory
variables, and how to interpret key regression results.
- Classical
regression model
- Difficulties
with regression models
- Interpreting
results
- Regression
coefficients
- The R-sq
statistic
- "t"
ratios and statistical significance
- Multicollinearity
- Log transformations
- Dummy
variables and seasonality
- Dynamic
(lagged) terms:
- Lagged
explanatory variables
- Lagged
dependent variable
- Lagged
error terms
- Model
building strategy
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Module 11: Dynamic Regression Case Study
This
module presents a guided tour from design to implementation
of a regression model. The participant will learn the various
tests a model must pass, options for forecasting the model's
explanatory variables, and issues in evaluation the forecasting
accuracy of the regression model. The module emphasizes what
can and what cannot be trusted in the information supplied by
forecasting software.
- Classical
model is the starting point
- Checking
for error autocorrelations
- Checking
for lagged variables
- Introducing
lagged variables
- Checking
transformations
- Finding
an acceptable model
- Interpreting
coefficients and elasticities
- Checking
goodness of fit (within sample)
- Checking
forecasting accuracy (out-of-sample)
- Forecasting
the explanatory variables
- Prediction
intervals (PIs): standard
- PIs when
explanatory variables are forecast
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Module 12: Forecasting with Econometric
Models
Many
dozens of econometric models attempt to forecast the macro economy:
income, price inflation, unemployment, etc. This module helps
the business analyst to understand the nature of econometric
forecasts and better judge the value of econometric forecasts
to the organization.
- Who makes
econometric forecasts?
- Characteristics
of econometric models:
- Multi-equations
- Feedback
effects
- Simultaneous
equations estimation
- Applications
of econometric models:
- Unconditional
forecasting
- Policy
simulations
- Linkage
equations
- Use of
judgment in econometric forecasts
- Accuracy
of econometric forecasts
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Module 13: Combining and Consensus Forecasts
Hundreds
of published articles show how and when the forecaster can benefit
from combining forecasts from different methods. This brief
module highlights the principles of combining forecasts. It
also looks at consensus forecasts and their track record.
- Motivations
for combining forecasts
- How to
combine forecasts: unweighted and weighted averages
- Does
combining improve accuracy?
- Consensus
forecasts
- Groupthink
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