Time of day impacts on machine productivity and value recovery in an off-forest central processing yard

New Zealand Journal of Forestry Science

Table 6 Regression model for scanning value recovery ($ m ⁻³ )

Variable¹	Coefficient	Standard error	t-statistic	p-value
Intercept	7.96	2.72	2.9	0.0035
Stem Size	57.76	1.94	29.8	<0.00001
Stem Size Squared	−6.56	0.38	−17.2	<0.00001
Group E Operators	6.64	0.89	7.5	<0.00001
SBandE²	3.77	1.09	3.4	0.00059
Time of Day³	−0.36	0.08	−4.5	<0.00001
Total degrees of freedom		F statistic		Adjusted R Square
2807		506.2		0.474

¹Stem size is the average stem size (m³) scanned during each hour. Group E was an indicator variable for three operators whose value recovery was different from the other two scanner operators.
²SBandE was an indicator variable for those hours in which a scheduled break occurred or in which end-of-shift work was undertaken.
³Time of day is based on a 24 hour clock; e.g. 4 = from 4.00 to 4.59 am, 16 = from 4.00 to 4.59 pm, etc.