X
Tests Part III
Contingency X
Test With Yates Correction
X
= (| ad-bc| - 1/2N)
N
(a+b)(a+c)(c+d)(b+d)
X
= (|2000 - 2700| - 112.5)
x 225
(110)(170)(115)(55)
X
= (700 - 112.5)
x 225
1,182,275,000
X = 0.66 with 1df; critical X
= 3.84 for 1df, a = 0.05
Because the calculated X
is less than the tabulated X,
then accept Ho: no interaction between factors.
Another way to calculate Contingency X.
Observed:
| Environment |
Dominant |
Recessive |
Totals |
| 1998 |
80 |
30 |
110 |
| 1997 |
90 |
25 |
115 |
| |
170 |
55 |
225 |
Expected: Use P(A) P(B) = P(A and B) when A and B are independent.
| Environment |
Dominant |
Recessive
|
Relative
Frequency |
| 1998 |
110
x 170 x 225
(225) |
110
x 55 x 225
(225) |
110
225 |
| 1997 |
115
x 170 x 225
(225) |
55
x 115 x 225
(225) |
115
225 |
| |
170
225 |
55
225 |
225 |
| |
Dominant |
Recessive |
| 1998 |
83.17 |
26.85 |
| 1997 |
86.92 |
28.05 |
