In this section we will consider the qualitative methods of investigation usually associated with case studies, although note that case studies may also involve the collection and analysis of quantitative data. Because a case study is flexible, a wide range of qualitative approaches can be used to collect data - including observation, interviews, discussions and documents - and you may well need to use a mixture of different methods to obtain the information you want. Your choice of methods is determined primarily by the research questions you are seeking to answer, but you will also need to take account of the time and resources you have available.