My original code is this below.
The result of the query of ther "for" give me 37 records.
The result of the output variable Y is 4. The right result for this
variable is not for.

begin
SOMA = 0.0;
Y = 4;
FOR
select
DPA.NOTA_PROVA
from DIARIO_PROVA_ALUNO DPA
where
DPA.NOTA_PROVA is not null and
DPA.ID_CURSO = :CURSO and
DPA.ID_DISCIPLINA = :DISCIPLINA and
DPA.ID_FASE = :FASE and
DPA.ID_TURMA = :TURMA and
DPA.NUMERO_PROVA = :NUMERO_PROVA
into :NOTA_PROVA
DO BEGIN
Y = Y+1;
X = NOTA_PROVA - MEDIA;
POTENCIA = POWER(X,2);
SOMA = SOMA + POTENCIA;
END
SOMA = SOMA / qtd_aluno;
DPM = SQRT(SOMA);
suspend;
end