1# Probabilistic 2Estimators that implement the Probabilistic interface have the `proba()` method that returns an array of joint probability estimates for every possible class or cluster number. Probabilities are useful for ascertaining the degree to which the estimator is *certain* about a particular outcome. A value of 1 indicates that the estimator is 100% certain about a particular class or cluster number. Conversely, a value of 0 means that the estimator is 100% certain that it's *not* that class or cluster number. When the probabilities are considered together they are called a *joint* distribution and always sum to 1. 3 4## Predict Probabilities 5Return the joint probability estimates from a dataset: 6```php 7public proba(Dataset $dataset) : array 8``` 9 10```php 11$probabilities = $estimator->proba($dataset); 12 13var_dump($probabilities); 14``` 15 16```sh 17array(2) { 18 [0] => array(2) { 19 ['monster'] => 0.975, 20 ['not monster'] => 0.025, 21 } 22 [1] => array(2) { 23 ['monster'] => 0.2, 24 ['not monster'] => 0.8, 25 } 26 [2] => array(2) { 27 ['monster'] => 0.6, 28 ['not monster'] => 0.4, 29 } 30} 31``` 32