great useit article on the correct usage of radio buttons and check boxes.
Ever since the first edition of Inside Macintosh in 1984, the rule has been the same for when to use checkboxes versus radio buttons. All subsequent GUI standards and the official W3C Web standards have included the same definition of these two controls:
- Radio buttons are used when there is a list of two or more options that are mutually exclusive and the user must select exactly one choice. In other words, clicking a non-selected radio button will deselect whatever other button was previously selected in the list.
- Checkboxes are used when there are lists of options and the user may select any number of choices, including zero, one, or several. In other words, each checkbox is independent of all other checkboxes in the list, so checking one box doesn't uncheck the others.
- A stand-alone checkbox is used for a single option that the user can turn on or off.
jakob adds 10 more guidelines such as visually group choices together with clear separation from other groups. and then goes on to make the case for interface standards:
Most important, following design standards enhances users' ability to predict what a control will do and how they'll operate it. When they see a list of checkboxes, users know that they can select multiple options. When they see a list of radio buttons, they know that they can only select one. (Of course, not every user knows this, but many do, especially since this has been a design standard since 1984.)