[The appraisal of reliability and validity of subjective workload assessment technique and NASA-task load index].
OBJECTIVE
To test the reliability and validity of two mental workload assessment scales, i.e. subjective workload assessment technique (SWAT) and NASA task load index (NASA-TLX).


METHODS
One thousand two hundred and sixty-eight mental workers were sampled from various kinds of occupations, such as scientific research, education, administration and medicine, etc, with randomized cluster sampling. The re-test reliability, split-half reliability, Cronbach's alpha coefficient and correlation coefficients between item score and total score were adopted to test the reliability. The test of validity included structure validity.


RESULTS
The re-test reliability coefficients of these two scales and their items were ranged from 0.516 to 0.753 (P < 0.01), indicating the two scales had good re-test reliability; the split-half reliability of SWAT was 0.645, and its Cronbach's alpha coefficient was more than 0.80, all the correlation coefficients between its items score and total score were more than 0.70; as for NASA-TLX, both the split-half reliability and Cronbach's alpha coefficient were more than 0.80, the correlation coefficients between its items score and total score were all more than 0.60 (P < 0.01) except the item of performance. Both scales had good inner consistency. The Pearson correlation coefficient between the two scales was 0.492 (P < 0.01), implying the results of the two scales had good consistency. Factor analysis showed that the two scales had good structure validity.


CONCLUSIONS
Both SWAT and NASA-TLX have good reliability and validity and may be used as a valid tool to assess mental workload in China after being revised properly.
Xiao
Yuan-mei
YM
Institute of Occupational Health, West China School of Public Health, Sichuan University, Chengdu 610041, China.
Wang
Zhi-ming
ZM
Wang
Mian-zhen
MZ
Lan
Ya-jia
YJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D016743:Mental Competency; D008875:Middle Aged; D016272:Occupational Health; D015203:Reproducibility of Results; D012494:Sampling Studies; D012647:Self-Assessment; D011795:Surveys and Questionnaires / Q000592:standards; D013647:Task Performance and Analysis; D016526:Workload