Job characteristics are believed to have an impact on stress and well being at work (Karasek & Theorell, 1990). The demands of the job on the one hand and the extent to which you have control over your own activities (decision latitude) on the other are two factors, which together define how stressful a job is. Those jobs, which are high demand, but offer limited control, are considered to be high-strain and carry an increased risk of job dissatisfaction, stress and burnout. Based on this theoretical framework, the Union of Belgian Banks sent out a research call to several institutions, with a bidding process based on criteria such as quality of the proposal, timing, and – above all – budget. The aim of the research was to carry out quantitative research to measure the relationship between job characteristics and job satisfaction in all Belgian banks (see Cambré et al., forthcoming). But in order to do this effectively, several methodological issues needed to be resolved during the research process. First of all, a research consortium was selected to conduct the research, or more precisely, the two highest ranked bidders were asked to jointly undertake the research. This was the outcome of a political decision by the banks, since the employers preferred one partner and the unions (employee representatives) preferred the other. The two competing research institutes, a private company specialising in stress at work and the Katholieke Universiteit Leuven (Belgium), were required to co-operate and develop a level of trust in order to conduct the research. For example, both research institutes had different ideas as to which scale should be used in the questionnaire. They could not just combine the scales or include both scales, simply because they are supposed to measure the same concept. Furthermore, this would also make the questionnaire too complex. Therefore, the research institutes had to combine their knowledge, look for compromises and jointly work on a shared vision, which is, to say the least, rather time consuming. A second obstacle that needed to be overcome was the sample. In total, 69,000 employees work for Belgian banks and it was decided that questioning all employees would be too complicated and too expensive. Therefore the research committee, consisting of representatives of the banks, the unions and the research consortium, opted for a cross-sectional design with a fixed sample of 15,000 employees. In this sample, the small banks were over-represented in order to be able to make conclusions at the level of each bank. Within each bank, the respondents were selected at random with no particular quota for gender, age or employee level. In the postal survey several steps were taken to improve the response rate. The survey was based on addresses which had been provided by the banks (name, language, address) and each employee randomly selected in the sample received a personalized envelope through regular mail, sent to him/her by the employer. The completed questionnaire needed to be returned (free of charge) through the internal post within each bank. This caused two problems: (1) a perceived lack of anonymity, because the employees received a personalized envelope; and (2) potential bias to the reliability and the response rate because the completed questionnaires were collected by the banks themselves. The researchers were able to overcome this by communicating clearly in a letter (1) that although the data collection was not completely anonymous (home address on envelope), the data analysis would be completely anonymous; and (2) that the completed questionnaires were collected by the bank but were transferred immediately to the researchers without being opened or read.
Sample size is n=15,000. Is this large sample really necessary? Discuss its relative and absolute size. What other options could have been taken?