Three-Dimensional Work Fatigue Inventory

German Workers: (Frone et al., 2018; n = 439; mean age = 39.24 years (12.32); female = 73%; average job tenure = 14.99 (11.48) years) 

• Mean Physical Fatigue score: 2.09 (0.91)
• Mean Mental Fatigue score: 2.10 (0.90)
• Mean Emotional Fatigue score: 1.67 (1.02)

Military Personnel: (Frone & Blais, 2019, n = 1375; male = 86%; Age < 35 years = 35%, 35-54 years = 55%, 55 years and older = 10%; stratified random sample of non-deployed regular force and primary reserve Royal Canadian Air Force [RCAF] personnel)  

• Mean Physical Fatigue score: 3.06 (1.25)
• Mean Mental Fatigue score: 3.08 (1.28)
• Mean Emotional Fatigue score: 2.50 (1.35)

US Workers: (Frone & Tidewell, 2015; n = 2,477; male = 52%, mean age = 40 years)

• Excellent for physical work fatigue scale (Cronbach’s alpha = 0.94*)
• Excellent for mental work fatigue scale (Cronbach’s alpha = 0.95*)
• Excellent for emotional work fatigue scale (Cronbach’s alpha = 0.96*)

German Workers: (Frone et al., 2018)

• Excellent for physical work fatigue scale (Cronbach’s alpha = 0.93*)
• Excellent for mental work fatigue scale (Cronbach’s alpha = 0.94*)
• Excellent for emotional work fatigue scale (Cronbach’s alpha = 0.96*)

Military Personnel: (Frone & Blais, 2019)

• Excellent for physical work fatigue scale (Cronbach’s alpha = 0.97*)
• Excellent for mental work fatigue scale (Cronbach’s alpha = 0.98*)
• Excellent for emotional work fatigue scale (Cronbach’s alpha = 0.99*)

Lebanese Physicians: (Sfeir et al., 2022; n = 401; male = 57.9%; mean age = 34.5 (13.48))

• Excellent for physical work fatigue scale (Cronbach’s alpha = 0.96*)
• Excellent for mental work fatigue scale (Cronbach’s alpha = 0.95*)
• Excellent for emotional work fatigue scale (Cronbach’s alpha = 0.97*)

*Scores higher than 0.9 may indicate redundancy in the scale questions.

U.S. Workers: (Frone et al., 2015)

Convergent validity:

• Physical and mental job demands primarily predicted physical (b  = 0.20, p < 0.001) and mental (b = 0.21, p < 0.001) work fatigue, respectively.
• Although emotional demands predicted higher levels of emotional work fatigue (b = 0.27, p < 0.001), they also predicted higher levels of physical (b = 0.22, p < 0.001) and mental work fatigue (b = 0.22, p < 0.001).
• Job autonomy was negatively related to physical (b = -0.18, p < 0.001) and mental work fatigue (b = -0.13, p < 0.05), but was unrelated to emotional work fatigue (b = -0.06, ns).

Discriminant validity:

• The items associated with the three hypothesized factors for work fatigue each loaded highly on its respective factor (0.82 to 0.90 for physical, 0.82 to 0.93 for mental, 0.80 to 0.93 for emotional; p < 0.001 for all loadings), thereby discriminating between physical, mental, and emotional work fatigue.
• Initiated and received job interdependence, lack of promotion opportunity, and friendship formation had nonsignificant and near-zero correlations with all three types of fatigue.

German Workers: (Frone et al., 2018)

Discriminant validity:

• The items associated with the three hypothesized factors for work fatigue each loaded highly on its respective factor (0.74 to 0.92 for physical, 0.77 to 0.93 for mental, 0.71 to 0.96 for emotional; p < 0.001 for all loadings), thereby discriminating between physical, mental, and emotional work fatigue.
• The correlations among the work fatigue factors support the discriminative validity of the three types of work fatigue:
  • Between physical and mental work fatigue (r = 0.59, p < 0.001)
  • Between physical and emotional work fatigue ( r = 0.50, p < 0.001)
  • Between mental and emotional work fatigue ( r = 0.65, p < 0.001) 

Content validity of the 3D-WFI was determined by a panel of 21 experts specializing in sociology and various areas of psychology (e.g., biological, clinical, developmental, and social), who had no affiliation with the present research project.  From the results of substantive agreement and substantive validity indices, Frone et al. (2015) concluded that the instrument has a high level of content validity.