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

New Zealand Journal of Forestry Science

Table 4 Regression model for scanning volume productivity (m ³ h ⁻¹ )

Variable¹	Coefficient	Standard error	t-statistic	p-value
Intercept	52.4	5.4	9.7	<0.00001
Stem size	28.9	1.7	16.8	<0.00001
Group A operators	−10.3	2.4	−4.4	0.00001
Group B operators	−17.2	2.4	−7.0	<0.00001
SBandE²	−33.4	2.4	−14.1	<0.00001
Time of day³	−1.0	0.2	−5.7	<0.00001
Total degrees of freedom		F statistic		Adjusted R Square
1890		129.1		0.254

¹Stem size is the average stem size (m³) scanned during each hour. Group A and Group B operators were indicator variables for single operators whose productivity was different from members within other groups, but not with members in the same group. Note that the default operator value was when two or more people scanned stems within the same hour.
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.