<?php

    echo $this->Form->create();
    $options = array('1' => '1', '2' => '2', '3' => '3', '4' => '4', '5' => '5', '6' => '6', '7' => '7', '8' => '8', '9' => '9', '10' => '10' );
    $attributes = array('legend' => false);

?>

<div class="answers">
    <?php
    echo $this->Form->radio('answer1', $options, $attributes);
    ?>
</div>

public $validate = array(
    'answer1' =>array(
        'rule' => 'notEmpty',
        'message' => 'Please choose an answer'
        )
);

$fields = array('answer1', 'answer2', 'answer3'); //all fields you need to validate
foreach($fields as $field) {
    $validate[$field] = array(
        'rule' => 'notEmpty',
        'message' => 'Please choose an answer'
    );
}

public $validate = array(
    'function' => array(
        'allowedChoice' => array(
            'rule'    => array('inList', array('1', '2', '3', '4')) //And so on
        )
    )
);