Table 2.
Factor pattern matrix for the PSQI two-factor solution and factor matrix for the PSQI single-factor solution, comparing two extraction methods.
| PSQI components | PCA extraction | ML extraction | ||
|---|---|---|---|---|
| PSQI two-factor solution | Factor 1 | Factor 2 | Factor 1 | Factor 2 |
| 1. Subjective sleep quality | 0.72 | -0.21 | 0.81 | 0.01 |
| 2. Sleep latency | 0.51 | -0.25 | 0.44 | 0.16 |
| 3. Sleep duration | 0.04 | -0.87 | 0.23 | 0.54 |
| 4. Habitual sleep efficiency | -0.03 | -0.91 | -0.09 | 1.04 |
| 5. Sleep disturbances | 0.74 | 0.06 | 0.59 | -0.03 |
| 6. Use of sleeping medication | 0.59 | 0.09 | 0.35 | 0.04 |
| 7. Daytime dysfunction | 0.72 | 0.02 | 0.62 | -0.08 |
| % of total variance | 41.07 | 15.96 | 21.38 | 24.49 |
| Interfactor correlation | -0.35 | 0.47 | ||
| PSQI single-factor solution | Factor 1 | Factor 1 | ||
| 1. Subjective sleep quality | 0.79 | 0.77 | ||
| 2. Sleep latency | 0.63 | 0.55 | ||
| 3. Sleep duration | 0.68 | 0.58 | ||
| 4. Habitual sleep efficiency | 0.65 | 0.53 | ||
| 5. Sleep disturbances | 0.61 | 0.54 | ||
| 6. Use of sleeping medication | 0.46 | 0.37 | ||
| 7. Daytime dysfunction | 0.62 | 0.55 | ||
| % of total variance | 41.07 | 31.95 | ||
Pittsburgh Sleep Quality Index, principal component analysis, and maximum likelihood. Factor loadings > .30 are in bold and were retained in the factor.