Evaluate checkboxes with params through post action in rails

Lately I was looking to evaluate the parameters from an post action.

The background is my questions model with four answers and one column with the a pointer to the right answer. My index.html view looks like this:

 <%= form_tag do %>  
 <table>  
  <% @questions.each do |question| %>  
      <tr>  
           <td>  
           <%= question.content -%>  
           </td>  
              <td>  
          <%= question.answer1-%>  
          <%= check_box_tag 'question_ids[]', question.id.to_s + '_1' -%>  
             </td>  
           <td>  
          <%= question.answer2-%>  
          <%= check_box_tag 'question_ids[]', question.id.to_s + '_2' -%>  
             </td>  
           <td>  
          <%= question.answer3-%>  
          <%= check_box_tag 'question_ids[]', question.id.to_s + '_3' -%>  
             </td>  
           <td>  
          <%= question.answer4-%>  
          <%= check_box_tag 'question_ids[]', question.id.to_s + '_4' -%>  
             </td>  
      </tr>  
  <% end %>  
 </table>  
 <%= flash[:message] %><br>  
  <%= submit_tag("Post") %>  
 <% end %>  

After I have checked some boxes a post action is done and per se the create method is called in the corresponding controller:

  # POST /diagnoses  
  # POST /diagnoses.json  
  def create  
      flash[:message] = params[:question_ids]  
       respond_to do |format|  
         format.html { redirect_to diagnoses_url }  
         format.json { head :no_content }  
        end  
  end  

The controller just puts the parameter on the screen as a flash message when the view is reloaded. NOTE: I put an extra flash message code in my view above.

Now I just have to evaluate it:

1. split id and answer number
2. compare answer number with column in model of given id