If you use buttons labeled "yes" and "no" then the radio buttons enter the text "yes" or "no" into the field, not the numbers 1 an 0.
You might choose to use a single value value list of just 1 and a check box field. Clicking the check box puts a 1 in the check box field (yes). Clicking it again clears the field (no). You can then resize the field to hide the '1' so that only the check box is visible.
Another option is to resize the field so that the radio buttons are listed vertically and so narrow that the values 1 and 0 aren't visible, then use layout text to label them yes or no.