| Expected Ratio | Yate's Correction | ||||
| A_ | aa | x Formula | X Formula | ||
| 1 : | 1 | x2 = | (A - a)2 | x2 = | (|A - a| - 1)2 |
| n | n | ||||
| 2 : | 1 | x2 = | (A - 2a)2 | x2 = | [|A - 2a| - 1.5]2 |
| 2n | 2n | ||||
| 3 : | 1 | x2 = | (A - 3a)2 | x2 = | [|A - 3a| - 2]2 |
| 3n | 3n | ||||
| 15 : | 1 | x2 = | (A - 15a)2 | x2 = | [|A - 15a| - 8]2 |
| 15n | 15n | ||||
| 9 : | 7 | x2 = | (7A - 9a)2 | x2 = | [|7A - 9a| - 8]2 |
| 63n | 63n | ||||
Short formula for 9:3:3:1
| X2 = | 16(a2 + 3b2 + 3c2 +9 d2) | - n | |
| 9n |
The terms a, b, c, d refer to the following observed numbers:
class A_B_ A_bb aaB_ aabb
observed a b c d
Short formula for testcross data: AaBb x aabb progeny
| X2A = | (a1 + a2 - a3 - a4)2 | for the A locus to test 1:1 ratio | |
| n | |||
| X2B = | (a1 - a2 + a3 - a4)2 | for the B locus to test 1:1 ratio | |
| n | |||
| X2L = | (a1 - a2 - a3 + a4)2 | to test for lack of independent assortment |
| n |
The terms a1, a2, a3, a4 refer to the following observed numbers for each class.
class AaBb Aabb aaBb aabb
observed a1 a2 a3 a4
Short formula for F2 data with four classes.
class A_B_ A_bb aaB_ aabb
observed a1 a2 a3 a4
X2A = |
(a1 + a2 - 3a3 - 3a4)2 | to test for 3:1 ratio for the A locus | |
| 3n | |||
| X2B = | (a1 - 3a2 + a3 - 3a4)2 | ||
| 3n |
| X2L = | (a1 - 3a2 - 3a3 + 9a4)2 | to test for lack of independent assortment | |
| 9n |
| X2 = | 16(a21 + 3a22 + 3a23 + 9a24) | - n Ho:9:3:3:1 fit |
| 9n |