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lnP2P1

lnP2P1 is a symbolic label rather than a universally defined constant. In documentation or code, it is typically used to denote the natural logarithm of a probability-related quantity named or indexed as P2P1. The exact meaning depends on the context in which it appears.

One common interpretation is that lnP2P1 means the natural logarithm of a probability ratio, specifically ln(P2/P1).

Another frequent reading occurs in stochastic models and machine learning, where P2P1 may denote a transition

In natural language processing and related fields, P2P1 can denote the probability of a specific event or

Because the symbol is context-dependent, readers should refer to the source material to determine the precise

See also: natural logarithm, log-likelihood, likelihood ratio, log-probability, Markov chain.

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This
log-likelihood
ratio
is
a
fundamental
quantity
in
statistics
and
hypothesis
testing,
where
it
is
used
to
compare
two
competing
models
or
hypotheses.
Because
probabilities
lie
in
[0,1],
the
log-ratio
is
non-positive
when
P2
≤
P1
and
becomes
more
negative
as
the
evidence
in
favor
of
P2
relative
to
P1
weakens.
probability
P(s2|s1)
from
state
s1
to
state
s2
in
a
Markov
chain
or
sequence
model.
In
that
usage,
lnP2P1
is
simply
the
log
probability
of
that
transition
and
is
often
used
to
score
sequences
in
log-space
for
numerical
stability,
converting
products
of
probabilities
into
sums.
token
pair,
with
lnP2P1
representing
the
log-probability
of
that
event.
Across
all
interpretations,
the
base
of
the
logarithm
is
the
natural
base
e.
definition
of
P2P1
in
a
given
setting.