Geostatistics - A Primer of GIS: Fundamental Geographic and Cartographic Concepts - page 287

Observed frequencies Expected frequencies

Forested Nonforested Forested Nonforested

High
precipitation

High
precipitation

Low
precipitation

Low
precipitation

Chi-Square Calulations

1 2 3 4 5

(O-E) 2 (O - E) 2 /E

Matrix cell Observed

frequencies

Expected
frequencies

a
b
c
d

Sum =

To determine the chi-square value we will use an interactive web application or a
published chart.

Calculate Yule's Q
Use the observed frequencies. A value close to +1 indicates a strong positive rela-
tionship between the independent and the dependent variables.
Yule's Q = ______________
a, b, c, d stand for cells in the observed frequency table
When you are finished, answer these questions.

Questions
1. How strong is the relationship between precipitation and forests in Minne-
sota?
2. What factors explain the values?
3. What other factors should be considered?
4. What problems do you see in the procedure for this exercise? Are the quad-
rants a good size for this analysis?