Algorithms for Point-Reduction of Individual Line Features

2002 ◽  
Vol 32 (4) ◽  
pp. 751-756 ◽  
Author(s):  
Christoph Kleinn ◽  
Berthold Traub ◽  
Christian Hoffmann

Length of line features, such as forest border, is among the ecologically interesting attributes estimated from forest inventories. In hilly terrain, observed line lengths must be corrected for slope. Contrary to the correction for standard area-related attributes (like volume per hectare), an overall correction of plot size is not sufficient, but the actual inclination of each individual line segment must be used for slope correction. This topic is discussed, and a mean correction factor is calculated as a function of terrain inclination assuming a uniform angular distribution of lines on the slope. Furthermore, the question is discussed whether the standard slope correction procedure for fixed-area circular field plots may possibly introduce a systematic error into the estimation of line length and also of standard area-related attributes. It is concluded that no relevant error is to be expected, neither with respect to point estimates nor to interval estimates. Data from the second Swiss National Forest Inventory serves for illustration.


1998 ◽  
Vol 500 (2) ◽  
pp. 1069-1069 ◽  
Author(s):  
Y. Ueda ◽  
H. Inoue ◽  
Y. Tanaka ◽  
K. Ebisawa ◽  
F. Nagase ◽  
...  
Keyword(s):  
X Ray ◽  

2021 ◽  
Vol 92 (4) ◽  
pp. 043512 ◽  
Author(s):  
E. P. Hartouni ◽  
R. M. Bionta ◽  
D. T. Casey ◽  
M. J. Eckart ◽  
M. Gatu-Johnson ◽  
...  

2020 ◽  
pp. 0193841X2097652
Author(s):  
Christina F. Mondi ◽  
Arthur J. Reynolds ◽  
Brandt A. Richardson

In a previous study of the Child-Parent Centers (CPC) education program, preschool participation was linked to a 4.6 percentage point reduction (26%) in depressive symptoms at ages 22–24 over the matched comparison group enrolling the usual programs. The present study reanalyzed these data in the Chicago Longitudinal Study to address potential attrition bias since more than a quarter of the sample was missing on the outcome. Using inverse probability weighting (IPW) involving 32 predictors of sample retention, findings for the 1,142 participants growing up in high-poverty neighborhoods indicated that CPC participation was associated with a 7.1 percentage point reduction (95% CI = [−9.7, −5.4]) in one or more depressive symptoms (39% reduction over the comparison group). Although this marginal effect was within the confidence interval of the original study (95% CI = [−9.5, 0.3]), the 54% increase in the point estimate is substantial and of practical significance, suggesting underestimation in the prior study. Alternative analysis of different predictors and IPW models, including adjustments for program selection and attrition together, yielded similar results. Findings indicate that high-quality early childhood programs continue to be an important strategy for the prevention of depression and its debilitating effects on individuals and families.


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