Table 2.

The light levels in the intervention group and the control group

	Mean (SD; min-max) vertical photopic lux	Mean (SD; min-max) vertical melanopic lux	Mean (SD; min-max) horizontal photopic lux	Mean (SD; min-max) horizontal melanopic lux	Mean (SD; min max) Kelvin vertical	Mean (SD; min-max) Kelvin horizontal
Intervention	1039 (225; 722–1242)	915 (174; 676–1050)	1842 (528; 1388–2585)	1680 (557; 1270–2488)	5369 (251; 5088–5641)	5521 (275; 5211–5879)
Control	242 (102; 134–368)	137 (90; 56–261)	343 (65; 259–408)	178 (52; 106–218)	3049 (470; 2707–3622)	3048 (397; 2707–3048)
p-value	.001	.000	.001	.002	.000	.000

Note: Vertical lux was measured 120 cm above the floor in the middle of the room in four directions that were averaged to produce the mean vertical illumination. Mean horizontal lux was calculated as the mean of measurements 80 cm above the floor in the middle of the room and 50 cm from the back wall. Mean lux values were calculated for the intervention and control group by averaging the values across clusters. Differences between groups tested with Student’s t-test