Walking around
neighborhoods, one quickly begins to see that the age of houses and their
associated architectural styles seem to be correlated with the quality, size
and, therefore, the price of houses. Do the age and value of houses correlate
statistically and spatially in Eau Claire?
Compare the maps of the median age of houses with the median
value of houses. Median means that half of the houses, in this case,
have lower and the other half have higher
values.
median age of
houses: For example, the median age of houses ranges from
1950-1975 in the dark green
areas.
median value of houses: For example, the median
value of houses ranges from $62,000-$70,000 in the dark green
areas.
A scattergram shows the statistical relationship between the median
age and median value of houses. The R square indicates that the
age of houses "explains" 45 percent of the value of houses. The value of
houses, of course, is also explained by other variables, such as quality
of houses, square feet, number of bedrooms, finished basements, etc. Each
symbol on the scattergram represents a census tract in the Eau Claire metro
area.
The regression
analysis produces residuals, which indicate the degree of "explanation."
Especially noteworthy are those residuals with the highest negative and positive
values because they indicate the "least fit" along the trend line on the
scattergram. Mapping the residuals result in this very interesting
map.
The age
of houses best "explains" the value of houses in the middle ranges of both
median ages and median values. In the older and new parts of the metro
area this correlation is the weakest. In the older parts of the city,
house values are higher than predicted relative to their actual value; and
in the new parts of the metro area, house values are lower than predicted.
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