Yes you should be using the rawValue .....I always set the RadioButtonList instead of the individual radio buttons. Also do an app.alert(RadioButtonList.rawValue) to ensure you are testing the right value.
It's called RadioButtonList a "group" of radio options.
In your example, in one RadioButtonList, you have 2 options: Yes and No. You should specify a value for each option in the RadioButtonList's Binding tab.
By doing this you're able to change the value at run time:
form1.subform.RadioButtonList.rawValue = "1"; // for Yes option.