public function automatedReadabilityIndex($strText = false)
    {
        $strText = $this->setText($strText);

        $score = Maths::bcCalc(
            Maths::bcCalc(
                4.71,
                '*',
                Maths::bcCalc(
                    Text::letterCount($strText, $this->strEncoding),
                    '/',
                    Text::wordCount($strText, $this->strEncoding)
                )
            ),
            '+',
            Maths::bcCalc(
                Maths::bcCalc(
                    0.5,
                    '*',
                    Maths::bcCalc(
                        Text::wordCount($strText, $this->strEncoding),
                        '/',
                        Text::sentenceCount($strText, $this->strEncoding)
                    )
                ),
                '-',
                21.43
            )
        );

        if ($this->normalise) {
            return Maths::normaliseScore($score, 0, $this->maxGradeLevel, $this->dps);
        } else {
            return Maths::bcCalc($score, '+', 0, true, $this->dps);
        }
    }