Table 16: SF-36 mental health scale Rasch analysis of standardised residual variance in Eigenvalue units for six waves of data collection.

WAVE 1WAVE 2WAVE 3
EigenvalueObservedExpectedEigenvalueObservedExpectedEigenvalueObservedExpected

Total raw variance in observations38.55100.00%100.00%41.29100.00%100.00%42.62100.00%100.00%
Raw variance explained by measures24.5563.70%63.70%27.2966.10%66.20%26.6262.50%62.50%
Raw variance explained by persons2.857.40%7.40%2.065.00%5.00%2.686.30%6.30%
Raw Variance explained by items21.7056.30%56.30%25.2361.10%61.20%23.9456.20%56.20%
Raw unexplained variance (total)14.0036.30%36.30%14.0033.90%33.80%16.0037.50%37.50%
Unexplained variance in 1st contrast6.2216.10%44.50%6.2215.10%44.40%7.0216.50%43.90%
Unexplained variance in 2nd contrast1.493.90%10.60%1.473.60%10.50%1.623.80%10.10%
Unexplained variance in 3rd contrast1.293.30%9.20%1.323.20%9.40%1.293.00%8.10%
Unexplained variance in 4th contrast0.812.10%5.80%0.852.00%6.00%1.052.50%6.60%
Unexplained variance in 5th contrast0.681.80%4.90%0.711.70%5.00%0.711.70%4.40%

WAVE 4WAVE 5WAVE 6
EigenvalueObservedExpectedEigenvalueObservedExpectedEigenvalueObservedExpected

Total raw variance in observations39.19100.00%100.00%37.79100.00%100.00%37.65100.00%100.00%
Raw variance explained by measures25.1964.30%64.50%23.7962.90%63.30%23.6562.80%63.20%
Raw variance explained by persons2.436.20%6.20%1.734.60%4.60%2.446.50%6.50%
Raw Variance explained by items22.7658.10%58.30%22.0658.40%58.70%21.2156.30%56.60%
Raw unexplained variance (total)14.0035.70%35.50%14.0037.10%36.70%14.0037.20%36.80%
Unexplained variance in 1st contrast6.1615.70%44.00%6.1016.10%43.60%5.7515.30%41.10%
Unexplained variance in 2nd contrast1.523.90%10.90%1.614.20%11.50%1.674.40%11.90%
Unexplained variance in 3rd contrast1.323.40%9.40%1.313.50%9.30%1.353.60%9.60%
Unexplained variance in 4th contrast0.802.00%5.70%0.792.10%5.60%0.852.30%6.10%
Unexplained variance in 5th contrast0.681.70%4.90%0.691.80%4.90%0.681.80%4.80%

Notes. > 60% unexplained variance in the Rasch factor; Eigenvalue in the first contrast <3.0; < 10% unexplained variance in the first contrast.