Agriculture Reference
In-Depth Information
The H-test
The H-test is appropriate for detecting in-range heterogeneity but may also be used to detect off-range het-
erogeneity. With the information below, it is possible to calculate the H-value for heterogeneity in seed lots.
No =
number of containers in the lot.
N =
number of independent container-samples.
n =
number of seeds tested from each sample (1000 for purity; 100 for germination; and 10,000
for other seed count, see 3.3).
X =
test result of the adopted attribute in a container-sample.
Σ =
symbol for sum of all values.
f
=
factor for multiplying the theoretical variance to obtain the acceptable variance (see Table
2C in ISTA, 2010).
∑
N
X
Observed variance of independent container-samples based on
all X-values in respect to the adopted attribute.
X=
V=
X.
(
100-X)
n
Acceptable variance of independent container-samples in respect
to number of other seeds.
. f
Mean of all X-values determined for the lot in respect to the
adopted attribute.
W=X.f
ﾠ
N(N-1)
V=
N X
2
-(X)
2
Observed variance of independent container-samples based on
all X-values in respect to the adopted attribute.
Heterogeneity can be calculated as follows:
¯
=
(ΣX)/N, the mean of all values of X (e.g., germ or purity test results) for the lot.
v =
[(
¯
•
(100 -
¯
)
/
n]
•
f acceptable variance for germination or purity.
W =
(
¯
•
f) acceptable variance for other seed counts.
V =
[NΣX
2
- (ΣX)
2
]
/
[N(N-1)], the observed (actual) variance of all results (all x - values) of a
test.
H (Heterogeneity) = (V
/
W) - f.
Negative values are reported as zero.
