ase study is a method of studying specific behaviours or problems for individuals or organizations. It is a method of collecting data using historical data, archival materials, interview observations, etc., and using reliable techniques to analyse an object to obtain a universal conclusion (Byrne& Humble,2007). The case study conducts in-depth research by selecting appropriate events, and draws some assumptions and conclusions through superficial phenomena as the basis for further research in the future.

For this study, case studies are a more appropriate method because of time and cost. It can also make the research of vocational education and training companies more specific and lay the foundation for later research. Qualitative research can be carried out through a small number of training companies, which can partly reflect the vocational education and training market.

In the case study, first choose a suitable vocational education and training company for research. Then determine the subject of the case study, go to the library or search for relevant information on the Internet, or go to the location of the company to conduct on-the-spot exploration and in-depth study of specific issues.

Advantages: Specific cases can make the understanding of the theory become sensible and specific, and enable the researchers to fully understand the theoretical understanding. (Byrne& Humble,2007)

Disadvantages: the cases themselves are individual cases, and each case has its own characteristics that cannot be duplicated, such as specific time, space environment and so on. The results of case studies are not easy to be generalized and lack of objectivity.

3.4.2 Questionnaire
The questionnaire survey method is a method for researchers to collect data, solicit opinions or understand the situation from the target group through questionnaires(Mathirajan,2006). The self-administered questionnaire has the characteristics of standardized access.

In this study, the questionnaire will be sent to the trainees. The question revolves around whether they feel that their abilities have improved after being trained. In what ways has it been improved and what has remained unchanged.
In this study, questionnaires will be sent to trainees. The questionnaire questions will revolve around whether they feel their abilities have improved after training. Where it has improved and where it has not changed.

When designing the questionnaire, take into account the time spent by the int