(byebug) criterios
  Criterio Load (0.3ms)  SELECT `criterios`.* FROM `criterios` WHERE `criterios`.`area_id` = 9
#<ActiveRecord::Associations::CollectionProxy [#<Criterio id: nil, nome: "Blah", descricao: "Blah", tipo_prova: "escrita", valor: 10.0, area_id: 9, created_at: nil, updated_at: nil>]>

(byebug) criterios.where(tipo_prova: "escrita")
  Criterio Load (0.3ms)  SELECT `criterios`.* FROM `criterios` WHERE `criterios`.`area_id` = 9 AND `criterios`.`tipo_prova` = 'escrita'
#<ActiveRecord::AssociationRelation []>