# cond.true: Number of individuals for which the condition is true. In riskyr: Rendering Risk Literacy more Transparent

## Description

`cond.true` is a frequency that describes the number of individuals in the current population `N` for which the condition is `TRUE` (i.e., actually true cases).

## Usage

 `1` ```cond.true ```

## Format

An object of class `numeric` of length 1.

## Details

Key relationships:

1. to probabilities: The frequency of `cond.true` individuals depends on the population size `N` and the condition's prevalence `prev` and is split further into two subsets of `hi` by the sensitivity `sens` and `mi` by the miss rate `mirt`.

Perspectives:

1. by condition:

The frequency `cond.true` is determined by the population size `N` times the prevalence `prev`:

` cond.true = N x prev`

2. by decision:

a. The frequency `hi` is determined by `cond.true` times the sensitivity `sens` (aka. hit rate `HR`):

` hi = cond.true x sens`

b. The frequency `mi` is determined by `cond.true` times the miss rate `mirt = (1 - sens)`:

` mi = cond.true x mirt = cond.true x (1 - sens)`

2. to other frequencies: In a population of size `N` the following relationships hold:

• `N = cond.true + cond.false` (by condition)

• `N = dec.pos + dec.neg` (by decision)

• `N = dec.cor + dec.err` (by correspondence of decision to condition)

• `N = hi + mi + fa + cr` (by condition x decision)

Current frequency information is computed by `comp_freq` and contained in a list `freq`.

## References

Consult Wikipedia: Confusion matrix for additional information.

`is_freq` verifies frequencies; `num` contains basic numeric parameters; `init_num` initializes basic numeric parameters; `freq` contains current frequency information; `comp_freq` computes current frequency information; `prob` contains current probability information; `comp_prob` computes current probability information.
Other frequencies: `N`, `cond.false`, `cr`, `dec.cor`, `dec.err`, `dec.neg`, `dec.pos`, `fa`, `hi`, `mi`
 ```1 2 3``` ```cond.true <- 1000 * .10 # => sets cond.true to 10% of 1000 = 100 cases. is_freq(cond.true) # => TRUE is_prob(cond.true) # => FALSE, as cond.true is no probability (but prev and sens are) ```