Tips for Effective Selection Options (Radio Buttons)
When giving users options on a form you can offer radio buttons, which allow for a single choice, or check boxes, which allow for multiple choices. Recently Nielsen Norman Group did some research that offers insight into the best way to present radio button options.
The key finding is that you should offer a default selection in most cases. Reasons to deviate or not: expedite tasks, the power of suggestion, user expectations, safety nets. Read the entire research findings.