On a level of an organisation, the bigger the sample, the more reliable and meaningful the survey results. Moreover, ideally, responses have to be balanced like the organisation. On the European level, the more responses there are in the survey, the better and more complete our understanding of the safety climate of European railways.
All the staff should be involved, including the non-safety and administrative personnel. The profile questions are designed to include such respondents.
Yes, it is highly advised, especially if they provide products and services which can impact safety, directly or indirectly.
There is no set minimum, and it also depends in the size of the organisation. A comprehensive picture requires involvement of all the department and units. Moreover, in order for ERA communicate the results to the partner organisation, we expect 9 respondents at least for each value of each question (if not, some grouping will be necessary). For more advanced analyses, more respondents are needed to ensure both anonymity and statistical reliability.
Yes, as union representatives contribute to the safety of all staff. In addition, they may promote the involvement of staff in the activity and help achieve a high response rate.