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. Author manuscript; available in PMC: 2023 Apr 5.
Published in final edited form as: Psychol Aging. 2021 Dec 30;37(2):149–162. doi: 10.1037/pag0000667

Table 2.

Mixed Model Results: Fixed Effects of Concurrent Daily Stressors and Within-Day Stressor Pile-Up on Negative Affect, Persisting Stressor Pile-Up Burden Estimated with an Exponential Decay Function

Stressor severity
 Stressor occurrence
Estimate SE P Estimate SE P
Fixed effects:
Exponential Coefficient α 0.395 0.139 0.005 0.491 0.165 0.003
Intercept β0 8.329 0.716 <.001 8.383 0.784 <.001
Stress Pile-up β1 0.906 0.158 <.001 4.388 0.709 <.001
Current Stressor β2 2.457 0.281 <.001 13.444 1.492 <.001
Current Stressor×Pile-up β3 0.336 0.101 0.001 17.156 3.841 <.001
Person-level Stress β4 0.525 0.067 <.001 25.868 4.473 <.001
Daytime β5 −0.227 0.030 <.001 −0.231 0.031 <.001
Random co/variances:
Var(α) 0.746 1.158 <.001 a 1.464 2.130 <.001a
Var(β0) 78.92 9.042 <.001b 96.803 11.066 <.001b
Var(β1) 1.418 0.293 <.001b 34.650 6.712 <.001b
Var(β2) 5.854 1.193 <.001b 221.52 38.923 <.001b
Var(β3) 0.409 0.194 <.001b 959.38 336.38 <.001b
Var(β5) 0.074 0.016 <.001b 0.085 0.018 <.001b
Cov(β0 β1) 0.521 1.066 1.000 a 6.535 5.977 0.317a
Cov(β0 β2) −0.019 2.083 1.000 a 12.183 13.732 0.317 a
Cov(β1 β2) 1.042 0.466 0.025 a 40.634 12.032 <.001 a
Cov(β0 β3) −0.966 0.782 0.046 a −39.327 38.530 0.317 a
Cov(β1 β3) 0.060 0.152 1.000 a 0.751 21.219 1.000 a
Cov(β2 β3) −0.789 0.361 0.014 a −222.63 82.617 0.003 a
Cov(β0 β5) −1.044 0.296 <.001 a −0.896 0.344 0.008 a
Cov(β1 β5) −0.034 0.051 1.000 a −0.199 0.242 0.317 a
Cov(β2 β5) −0.225 0.101 0.025 a −1.893 0.618 0.002 a
Cov(β3 β5) 0.075 0.038 0.046 a 4.562 1.759 0.005 a
Var(Residual) 58.187 1.080 0.005 58.999 1.104 <.001
Model R 2 0.360 0.351
Pile-up R 2 0.142 0.140

Notes. For all estimates the gradient of the negative log-likelihood function was sufficiently small (< 0.00005) to indicate accurate estimates at convergence (SAS Institute Inc., 2015). The estimates for exponential coefficient α and Var(α) are functions of estimates of basic model parameters γ and Var(γ), with γ = −1.808 (SE = 0.098, P < .001) and Var(γ) = 1.756 (SE = 0.711) for severity, and γ = −1.690 (SE = 0.109, P < .001) and Var(γ) = 1.967 (SE = 0.688) for occurrence. R2 computation: Reduction of within-person residual variance, compared with the random intercept only null model (Model R2) and with the model with β1 and β3 pile-up effects excluded (Pile-up R2).

a

P-values from likelihood-ratio (−2LL-differences, df = 1) test.

b

P-values from likelihood-ratio test for total random component (i.e., random variance and all 5 covariances including the component, df = 6).