Description of the workplace factors and attitudes measured
| Factor | How it was measured |
|---|---|
| Workplace factors | |
| Mine type | Open-cut or underground mining |
| Commute type | A single-item question regarding commute arrangements:
|
| Years working in mining | A single-item question that determined length of time working in the industry. |
| Time to camp (long-distance commute only) | A measure of the duration of time to reach the mine site camp from the participant's home. For multivariate analysis, we used dummy coding for all daily commute employees, with each participant given the mean response score of long distance commute participants. |
| Daily commute time (daily commute participants only) | A measure of the time taken to drive to work each day. For multivariate analysis, we used dummy coding for all long-distance commute participants, with each participant given the mean response score of daily commute participants. |
| Employment category | A single-item question about the employees’-specific occupational role from a list including: manager; professional; technician or trade worker; machinery operator and driver/labourer; or administration/other. |
| Employment status | A single-item question that determined if participants worked full-time or part time. |
| Principal employee vs contractor | A single-item question to identify participants employed by the mine (principal employee) or as a contractor. |
| Shift type | Asked participants to indicate whether they commonly work on a rotating shift pattern (mixture of day/evening/night shifts) or a regular shift (day shift only, or night shift only). |
| Shift length | Number of hours of the participant’s most common shift |
| Proportion of days at work | Using the participant's typical roster, the proportion of time at work was a ratio of the number of consecutive days at work and the number of consecutive days off work. |
| Attitudes | |
| Satisfaction with work | An aggregate score based on the average responses given to seven items scored on a 5-point scale ranging from 1: ‘very dissatisfied’ to 5: ‘very satisfied’. Items include satisfaction with: your usual take-home pay; your work prospects; the people you work with; physical work conditions; the way your section is run; the way your abilities are used; and the interest and skill involved in your job (α=0.83). |
| Concern about losing job | A single item measured on a 5-point scale that asked participants to rate their level of concern about losing their job. Scores ranged from 1: ‘not at all’ to 5: ‘extremely worried’. |
| Work in mining for financial reasons | Aggregate score based on average response to three items scored on a 5-point scale ranging from 1: ‘strongly disagree’ to 5: ‘strongly agree’. Items include: the pay is the main reason I work in coal; I have financial commitments that mean I have to continue to work in coal mining because of the salary levels; I would prefer to work in another job but cannot afford to leave because of my financial commitments (α=0.68). |
| Work in mining because I love the work, and the roster suits my family | Average response to two items scored on a 5-point scale ranging from 1: ‘strongly disagree’ to 5: ‘strongly agree’. Items include: I work in coal because I love the work; the roster schedule suits my family and me (α=0.40). |
| Perception of the mine’s commitment to mental health | Average response to five items scored on a 5-point scale ranging from 1: ‘strongly disagree’ to 5: ‘strongly agree’. Items include: this mine would be flexible in offering work adjustments to someone with a mental health problem; this mine provides education and training to supervisors and managers about mental health; the managers at this mine have a good understanding of mental health issues; the mine provides education to employees about mental health; our workplace policies support the mental health of mine employees (α=0.89). |
| JCQ21 | Items from the JCQ were used to measure the job–strain ratio, which was calculated using the formula: job–strain ratio=mean of psychological demand/(the mean of decision authority and skill discretion). Thus, participants with a ratio score of 1 indicate balance between psychological demands and decision control; a ratio score above 1 indicates that psychological demands outweigh decision control; a ratio score below 1 indicates decision control is greater than psychological demands. |
| Perceived control over work | The average response to the two items reflecting perceived control scored on a 5-point scale ranging from 1: ‘none’ to 5: ‘complete control’. Items include: the specific shifts that you work; the specific start and finish times that you work (α=0.84). |
DIDO, drive-in drive-out; FIFO, fly-in fly-out; JCQ, Job Content Questionnaire.