Qualitative data comprises recordings of individual perceptions - the meaning that events or incidences have to those involved. It is held as notes of interviews or observations, statements from people, etc. The researcher is concerned with gaining insight through evaluation and comparison of the evidence, rather than with providing ‘scientific' evidence. The conclusions still need to be systematically substantiated by the available data.
Quantitative and qualitative data both have strengths and weaknesses, depending on the issue addressed, and are often fruitfully used together.