Open questions involve the use of the words ‘who’, ‘what’, ‘where’, ‘why’, ‘when’ and ‘how’, and elicit more substantive answers than closed questions. For this reason, enquiry documents like a Request for Information often use combinations of questions to gather information. For example, ‘Do you have a quality policy?’ is a closed question, but when coupled with ‘How does your quality system ensure consistent performance standards which meet the customer’s needs?’ becomes more powerful. See also Question, Probing.