[Javascript] Javascript - Form value undefined

[Tim Burgan]

Hello,

I'm doing a basic JavaScript course at the moment - I'm trying to use
logical operators at the moment, but I've got stuck right at the beginning
with submitting a value from a form into JavaScript.

I've stripped the page down to 2 forms that are identical except from the
data input methods - 1 works (text inputs), 1 doesn't (radio inputs).

<http://www.greaterthani.com/05_programming/week5help.htm>

The form with the radio button displays a result of 'undefined', when it
should be either 0 or 0.25

Can someone please take a look at this to kelp me out?

Thanks for your time
Tim Burgan