You did it wrong according to the syntax.
Use the following, which I tested on localhost:
echo $this->Form->checkbox('stats',array(
'value' => '1',
'hiddenField' => true,
));
: hiddenField' => '0', , 0, PHP false ( PHP). .
:
<input type="hidden" name="data[CourseCategory][stats]" id="CourseCategoryStats_" value="0">
<input type="checkbox" name="data[CourseCategory][stats]" value="1" id="CourseCategoryStats">