Table 2. Results of multilevel modeling for perceived physical exertion (PE).

	PE0: Intercept Only			PE1: + Level 1 Predictors			PE2: + Level 2 Predictorse			PE3: + Random Coefficients			PE4: + Cross-level Interactions
Fixed Componentsa,b
Predictor	ß [S.E.]	df	p	ß [S.E.]	df	p	ß [S.E.]	df	p	ß [S.E.]	df	p	ß [S.E.]	df	p
1. Intercept	-0.01 [0.14]	54	.97	-0.01 [0.11]	42	.92	-	-	-	-0.01 [0.11]	43	.9	-0.04 [0.11]	43	.70
2. Entropy of transitions				0.15 [0.10]	42	.11	-	-	-	0.14 [0.09]	43	.11	0.15 [0.08]	43	.06
3. Burstiness of transitions				-0.07 [0.12]	42	.57	-	-	-	-0.6 [0.10]	43	.58	-0.03 [0.09]	43	.76
4. Time speaking outside of main work areas				-0.02 [0.10]	42	.84	-	-	-	0.03 [0.09]	43	.71	0.03 [0.09]	43	.78
5. Volume while speaking at nursing stations				0.07 [0.09]	42	.44	-	-	-	0.02 [0.14]	43	.87	0.05 [0.13]	43	.68
6. Time at nursing stations				0.16 [0.10]	42	.14	-	-	-	0.16 [0.10]	43	.10	0.17 [0.09]	43	.08
7. Environmental noise in service areas				0.19 [0.09]	42	.04	-	-	-	0.19 [0.08]	43	.03	0.18 [0.08]	43	.03
8. Time walking in patient rooms				0.09 [0.10]	42	.36	-	-	-	0.12 [0.09]	43	.18	0.12 [0.09]	43	.18
9. Temperature in service areas				-0.04 [0.09]	42	.62	-	-	-	-0.04 [0.09]	43	.65		-
10. Entropy of transitions x Burstiness of transitions				0.19 [0.09]	42	.04	-	-	-	0.23 [0.07]	43	.004	0.22 [0.07]	43	.003
11. Time speaking outside of main work areas x Time at nursing stations				0.38 [0.11]	42	< .001	-	-	-	0.38 [0.10]	43	< .001	0.37 [0.09]	43	< .001
12. Environmental noise in service areas x Time walking in patient rooms				-0.23 [0.10]	42	.02	-	-	-	-0.21 [0.08]	43	.01	-0.19 [0.08]	43	.02
13. Volume while speaking at nursing stations x Temperature in service areas				-0.14 [0.07]	42	.04	-	-	-	-0.02 [0.08]	43	.86	-	-
14. Average patient load													-0.05 [0.11]	33	.68
15. Average patient load x Volume while speaking at nursing stations													0.30 [0.13]	43	.02
Random Components
Between shift variance (σ2e)	0.55 [0.74]			0.19 [0.45]			-	-		0.26 [0.51]			0.25 [0.50]
Within shift / residual variance (σ2u0)	0.42 [0.65]			0.32 [0.56]			-	-		0.16 [0.40]			0.20 [0.45]
Slope variation (Volume while speaking at nursing stations)										0.27 [0.52]			0.16 [0.40]
Variance Modelledc
Level 1: R2Within Shift				0.24			-	-		0.62			0.52
Level 2: R2Between Shift				0.65			-	-		0.53			0.55
Ran. Coef.: R2 Slope: Volume spkng at RN statns										0			0.41
Model Fit
Deviance (-2 * Log likelihood ratio)d	226.59			183.34						174.25			168.55
L. Ratio	χ2(1) = 24.98, p < .001			χ2(12) = 43.25, p < .001						χ2(2) = 9.08, p < .05			f

^aThere were 89 shift segments nested within 35 shifts.

^b Terms 2–9 are Level 1 main effects; Terms 10–13 are level 1 interactions; Term 14 is a Level 2 main effect; Term 15 is a cross-level interaction.

^cProportion of variance explained for Level 1 (within shifts) and Level 2 (between shifts) were calculated relative to PE₀, th model with only a grouping variable; Proportion of slope variation explained was calculated relative to PE₃, the model with random coefficients, but no cross-level interactions.

^dReduction in model deviance was tested as follows: PE₀ contained only the shift grouping variable and was tested against a model without the grouping variable; PE₁ included Level 1 sensor-based measures and was tested against PE₀; PE₂ included Level 2 task demand fixed effects and was compared to PE₁; PE₃ included random coefficients for Level 1 sensor-based measures and was evaluated relative to PE₂, the model without random coefficients; PE₄ included cross level interactions between Level 1 and Level 2 predictors and was evaluated relative to PE₃.

^eNo Level 2 task demand variables were retained as significant in PE₂. Therefore, PE₂ = PE₁.

^fFor PE₄, model deviance was reduced, but model complexity (due to the loss of degrees of freedom by the inclusion of nonsignificant main effects for significant interactions) precluded significance testing