Lemma 4.1
(Shearer)
.
Assuming that:
X
=
(
X
1
,
…
,
X
n
)
a random variable
A
a family of subsets of
[
n
]
such that every
i
∈
[
n
]
belongs to at least
r
of the sets
A
∈
A
Then
H
[
X
1
,
…
,
X
n
]
≤
1
r
∑
A
∈
A
H
[
X
A
]
.