
196 Practical Spreadsheet Risk Modeling for Management
6.7 Fourth Example: Home Prices and Multivariate Time Series
In Chapter 5 we looked at the importance of modeling relationships between
uncertain variables that are represented by probability distributions. In sim-
ilar fashion, we must be aware that there can also be a relationship between
random variables being modeled by a time series. These multiple time series,
while uctuating over time (due to randomness, trends, and seasonality),
may do so in a related fashion. For example, we now know that geographic
housing markets are somewhat related to one another. The relationship is
not