l - People

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The argument of the log is the ratio of the observed frequency of occurrence of classes of
amino acids
likelihood ratio
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a c in hinges, over the expected. Note that this argument is close to the
p(ac h)
used in Bayesian statistics[46] because H is so small
p(ac ~ h)
compared to D. The quantity HI yields an intuitive measure of the enrichment of certain
classes ! of residues in hinges, with positive numbers indicating enrichment and negative
numbers indicating scarcity. Just because the HI is nonzero, however, does not mean that
the differential representation has statistical significance. To establish the latter, we
considered two statistical hypotheses:
H 0 : The null hypothesis.
Assume
hc is a randomly distributed random variable with mean µ h. The null
hypothesis states that:
µ h = dc " H
D
If this is true, then the hinge set is chosen without replacement in an unbiased fashion
from the dataset, and p(ac h)is given by the hypergeometric distribution (Equation 3).
H , The alternate ! hypothesis.
1
This states that:
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