Using multiple-answer questions when unsuitable
When only one answer is sensible, for example when defining agreement (on a scale from 1 to 5) or frequency (e.g. daily, weekly, monthly, seldom, never), it is completely unacceptable to use the multiple-answer (checkbox) question type.
In all such cases, only one possible answer must be permitted by using the single-answer (radio button) question type. Mistakes of this type are elementary and are often made by beginners.