Reliability and Validity of the 4-Item Version of the Korean Perceived Stress Scale.

This study was designed to evaluate the reliability (internal consistency, reproducibility over time, and measurement precision) and validity (factorial, convergent, and concurrent validity) of the 4-item Korean Perceived Stress Scale in comparison to the 10-item Korean Perceived Stress Scale. Participants were 650 students from seven schools of nursing in South Korea. Measures included Korean versions of the Perceived Stress Scale, the Pittsburgh Sleep Quality Index, and a single-item quality-of-life measure. The 4-item Perceived Stress Scale had lower Cronbach alpha than the 10-item Perceived Stress Scale (.65 vs. .80), but its item-total correlations (.35-.47) and split-half coefficient (.81) were comparable to the 10-item Perceived Stress Scale (item-total correlations = .20-.56; split-half coefficient = .82). Reproducibility of the 4-item scale after a 1-week interval (r = .67, ICC absolute agreement = .64) was similar to the 10-item scale (r = .70, ICC absolute agreement = .65). The standard error of measurement was slightly higher in the 4-item scale. Scale constructs of the two were identical in exploratory factor analysis. The two scales were highly correlated (r = .93) and showed similar levels of concurrent validity with sleep quality and quality of life. In conclusion, the 4- and 10-item Korean Perceived Stress Scale are similar in psychometric qualities.