Real-Life Math -- Solution
You've gathered this information for a block of houses on Rose Avenue.
There are nine houses and these are their household incomes: $35,000, $38,750,
$45,000, $33,500, $42,850, $48,750, $32,000, $670,000 and $31,000.
To figure out an average, you add up all the figures, and then divide
by the number of entries that you have:
Average = (35,000 + 38,750
+ 45,000 + 33,500 + 42,850 + 48,750 + 32,000 + 670,000 + 31,000) / 9
Average
= $108,538.89
So the average is $108,538.89.
To find the median value, you put the numbers in sequential order,
and then pick the middle number:
31,000, 32,000, 33,500, 35,000, 38,750,
42,850, 45,000, 48,750, 670,000
The middle number, or the median value,
of these numbers is $38,750.
It's better to use the median rather than the average when referring
to the household incomes on this street because the very high income, $670,000,
throws off the other numbers in the small group. The median usually works
better than the average when working with a small group of numbers.
If you were gathering household income statistics for all of Texas,
it would be better to use the average rather than the median.
"I'm not a strong math person, but math courses help in a lot of
the analysis that's done, especially as you get into aerial and satellite
imagery, and with the photo interpretation," says GIS expert Shannon White.
"You've got a lot of analysis that requires math," she adds. "They
need to understand some statistics, some calculus. But that's not required
of all jobs in GIS, so in some ways you can pick and choose."
"Without
numbers there is no GIS," says GIS expert Joseph Kerski. "Behind every point
or line is a number. Behind every satellite image is a number.
"I'd
say math is a critical skill for sure," Kerski adds. "It's all based on mathematical
models of the Earth's shape, and the surveying part of GIS is all based on
trigonometry, so math is critical, and sadly a lot of people
using GIS are weak in math."