The assumption of independence between BFTC measurements is likely to be violated if the sale of chips occurs at a different time than the sale of lumber.
The objectives of this paper were to determine: a) the distributional properties of BFTC ratio; b) if a negative autocorrelation exists between board footage and ton of chips; c) the appropriate diagnostics for BFTC ratio to determine abnormal deviation from mean process performance; and, d) if differences in BFTC models between species exist.
Histograms were charted to visually determine if normality existed for BFTC.
One reason for the non-normal distribution was the fact that the mill could never produce a BFTC below zero, thus skewing the histogram left.
Another concern is that the BFTC distributional properties will change from time to time, especially if a group of small- or large-diameter logs are run consecutively or nearly so.
Since mean log diameter can be dynamic, one could benefit by monitoring the diameter of every log coming in to account for the influence of log diameter on BFTC ratio.
However, after some investigation, this decreased variability was probably attributable to the fact that the mill consistently saw higher mean log diameters for oak than for poplar or pine, resulting in a decrease in BFTC error.
However, should a small sawmill be able to afford a weight scale, then a daily account of BFTC could be made.
BFTC ratio did not follow a normal distribution for any of the three major species processed at this sawmill.
Finally, it should be noted that the BFTC ratio should not supercede the profitability of the mill.