Значение из формы JavaScript

Я создаю форму, которая позволяет рассчитать рейтинг слона: https://jsfiddle.net/molecoder/1oqxsw81/.

Пользователь может выбирать между 4 вариантами, и каждый из этих вариантов (0 см, 1-2 см, ...) имеет соответствующее значение.

Вот код HTML для формы:

<form action = "" id = "bishopform" onsubmit = "return true;">
     <div>
         <fieldset>
            <legend>Bishop score</legend>
            <p>(modify one field to see the score)</p>
            <div id = "bishopScore"></div>
            <label><b>Cervical Dilatation</b></label><br/>
            <label class='radiolabel'><input type = "radio"  name = "selectedcervicaldilatation" value = "cerdi1" onclick = "calculateTotalBishop()"/>0 cm</label><br/>
            <label class='radiolabel'><input type = "radio"  name = "selectedcervicaldilatation" value = "cerdi2" onclick = "calculateTotalBishop()" checked/>1-2 cm</label><br/>
             <label class='radiolabel'><input type = "radio"  name = "selectedcervicaldilatation" value = "cerdi3" onclick = "calculateTotalBishop()" />3-4 cm</label><br/>
             <label class='radiolabel'><input type = "radio"  name = "selectedcervicaldilatation" value = "cerdi4" onclick = "calculateTotalBishop()"/>5-6 cm</label><br/>
              <br/>
           </fieldset>
      </div>
</form>

Вот код JavaScript для обработки выбора:

 var cervical_dilatation = new Array();
 cervical_dilatation["cerdi1"]=0;
 cervical_dilatation["cerdi2"]=1;
 cervical_dilatation["cerdi3"]=2;
 cervical_dilatation["cerdi4"]=3;

 // getCervicalDilation() finds the points based on the answer to "Cervical Dilation".
// Here, we need to take user's the selection from radio button selection
function getCervicalDilation()
{  
    var cerdiPoints=0;
    //Get a reference to the form id = "bishopform"
    var theForm = document.forms["bishopform"];
    //Get a reference to the answer the user Chooses name=selectedcervicaldilatation":
    var selectedCervicalDilation = theForm.elements["selectedcervicaldilatation"];
    //Here since there are 4 radio buttons selectedCervicalDilation.length = 4
    //We loop through each radio buttons
    for(var i = 0; i < selectedCervicalDilation.length; i++)
    {
        //if the radio button is checked
        if (selectedCervicalDilation[i].checked)
        {
            //we set cerdiPoints to the value of the selected radio button
            cerdiPoints = cervical_dilatation[selectedCervicalDilation[i].value];
            //If we get a match then we break out of this loop
            //No reason to continue if we get a match
            break;
        }
    }
    //We return the cerdiPoints
    return cerdiPoints;
}

function calculateTotalBishop()
{
    //Here we get the Bishop Score by calling our function
    //Each function returns a number so by calling them we add the values they return together
    var bishopScore = 3*getCervicalDilation() + 1;

    //display the result
    var divobj = document.getElementById('bishopScore');
    divobj.style.display='block';
    divobj.innerHTML = bishopScore+"% likelihood that induction will be successful";

}

По какой-то конкретной причине я не могу увидеть результат выбора пользователя.

Как это исправить?