prev defines a condition's prevalence value
(or baseline probability):
The probability of the condition being
An object of class
numeric of length 1.
Understanding or obtaining the prevalence value
prev is the (non-conditional) probability:
prev = p(condition = TRUE)
or the base rate (or baseline probability) of the condition's occurrence or truth.
In terms of frequencies,
prev is the ratio of
hi + mi)
hi + mi +
fa + cr):
prev = cond_true/N = (hi + mi)/(hi + mi + fa + cr)
prev classifies a population of
by condition (
prev = cond_true/N).
prev is the "by condition" counterpart
ppod (when adopting a "by decision" perspective) and
acc (when adopting a "by accuracy" perspective).
base rate of condition,
rate of condition
= TRUE cases.
prev is often distinguished from the incidence rate
(i.e., the rate of new cases within a certain time period).
prev is a feature of the population
and of the condition, but independent of the decision process
or diagnostic procedure.
While the value of
prev does not depend
on features of the decision process or diagnostic procedure,
prev must be taken into account when
computing the conditional probabilities
(as they depend on
Consult Wikipedia for additional information.
prob contains current probability information;
num contains basic numeric variables;
init_num initializes basic numeric variables;
comp_prob computes derived probabilities;
comp_freq computes natural frequencies from probabilities;
is_prob verifies probabilities.
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