Questions can be skipped by anonymous users but not by authenticated users

I've done a multiple choice quiz site (13 quizzes w/ 10qs each) and have set the questions to not be skippable, which when logged in as admin they aren't, but anonymous users can skip questions. I've looked in the "multichoice.classes.inc" file and found this snippet:

/**
* Implementation of isValid
*
* @see QuizQuestionResponse#isValid()
*/
public function isValid() {
if ($this->question->choice_multi) return TRUE;
if (empty($this->user_answer_ids)) return t('You must provide an answer');
return TRUE;
}

I'm assuming this is the validation, why can questions be skipped by non-logged in users but not by logged in users? I need the questions to be non-skippable by all users is this an error or a setting?

thanks for any help!