Real-Life Math
GIS uses some sophisticated math in order to display a map of a
round planet on flat paper. In addition to computer map work, there's a large
amount of statistical number crunching that has to be done.
This afternoon,
you're trying to gather some statistics on household incomes for a group of
nine homes on Rose Avenue. You'll be using these statistics later to show
the income bracket of the people who live in the neighborhood. This will help
real estate agents know who is likely to want to buy a house in the area.
Here
are some definitions you need to know:
Average: To figure out
an average, you add up all the figures, and then divide by the number of entries
that you have.
Median value: To find the median value, you
put the numbers in sequential order, and then pick the middle number.
The
average is easier to compute and works nicely with very large number sets.
The median, however, works better (and is more accurate) with small number
sets as it tends to eliminate the influence of very large or very small numbers
in relation to the rest of the group.
This is the information that
you've gathered for the block of nine houses on Rose Avenue.
These are their household incomes: $35,000, $38,750, $45,000, $33,500, $42,850,
$48,750, $32,000, $670,000 and $31,000.
What is the average household income for this street?
What is the median household income for this street?
Do you think it's better to use the average or the median when referring
to the household incomes on this street?
If you were gathering household income statistics for all of Texas,
would it be better to use an average or a median?