scholarly journals Double Sampling Saves Time When Cruising Appalachian Hardwoods

1996 ◽  
Vol 13 (3) ◽  
pp. 116-118 ◽  
Author(s):  
Paul R. Merten ◽  
Harry V. Wiant ◽  
John C. Rennie
Keyword(s):  
Standard Errors ◽  
Double Sampling ◽  
Point Sampling ◽  
Significant Bias ◽  
Volume Estimates ◽  
Appalachian Hardwoods

Abstract Simulations based on data collected in five Appalachian hardwood sawtimber-size stands indicate double sampling using point sampling (BAF 10 and 20) compared to conventional point sampling would save 24 to 47% of time in the field. There was no significant bias in volume estimates using double sampling, and standard errors were within about 1% of those obtained with conventional point sampling. North. J. Appl. For. 13(3):116-118.

scholarly journals Comparing Double-Sampling Efficiency Using Various Estimators with Fixed-Area and Point Sampling

2008 ◽  
Vol 25 (2) ◽  
pp. 99-102 ◽  
Author(s):  
Christopher A. Dahl ◽  
Brent A. Harding ◽  
Harry V. Wiant
Keyword(s):  
Double Point ◽  
Double Sampling ◽  
Sampling Efficiency ◽  
Sample Sizes ◽  
Sampling Errors ◽  
Point Sampling ◽  
Sampling Schemes ◽  
Fixed Area ◽  
Multiple Sample ◽  
Volume Estimates

Abstract In this study, we compare the efficiency of double sampling using point sampling and fixed-area plots for sawtimber volume estimates in a mixed-hardwood, oak-dominated stand. Multiple sample sizes and combinations were evaluated to determine optimum double-sample ratios. Results indicatedthat double, point-sampling schemes are more efficient in terms of field time and sampling errors than double-sampling schemes incorporating fixed-area plots. Data suggested that the most efficient ratio of measured and nonmeasured points with double sampling varies on the basis of the nonmeasuredvariable used and desired SE percentage levels for the inventory.

Multi-Center Calibration of the Second Reference Material for Thromboplastin, Rabbit, Plain, Coded CRM 149R

1991 ◽  
Vol 65 (03) ◽  
pp. 263-267 ◽  
Author(s):  
A M H P van den Besselaar ◽  
R M Bertina
Keyword(s):  
Reference Material ◽  
Standard Error ◽  
Standard Errors ◽  
Sensitivity Index ◽  
Long Term Stability ◽  
Significant Bias ◽  
The Mean ◽  
The Relationship ◽  
International Sensitivity Index

SummaryIn a collaborative trial of eleven laboratories which was performed mainly within the framework of the European Community Bureau of Reference (BCR), a second reference material for thromboplastin, rabbit, plain, was calibrated against its predecessor RBT/79. This second reference material (coded CRM 149R) has a mean International Sensitivity Index (ISI) of 1.343 with a standard error of the mean of 0.035. The standard error of the ISI was determined by combination of the standard errors of the ISI of RBT/79 and the slope of the calibration line in this trial.The BCR reference material for thromboplastin, human, plain (coded BCT/099) was also included in this trial for assessment of the long-term stability of the relationship with RBT/79. The results indicated that this relationship has not changed over a period of 8 years. The interlaboratory variation of the slope of the relationship between CRM 149R and RBT/79 was significantly lower than the variation of the slope of the relationship between BCT/099 and RBT/79. In addition to the manual technique, a semi-automatic coagulometer according to Schnitger & Gross was used to determine prothrombin times with CRM 149R. The mean ISI of CRM 149R was not affected by replacement of the manual technique by this particular coagulometer.Two lyophilized plasmas were included in this trial. The mean slope of relationship between RBT/79 and CRM 149R based on the two lyophilized plasmas was the same as the corresponding slope based on fresh plasmas. Tlowever, the mean slope of relationship between RBT/79 and BCT/099 based on the two lyophilized plasmas was 4.9% higher than the mean slope based on fresh plasmas. Thus, the use of these lyophilized plasmas induced a small but significant bias in the slope of relationship between these thromboplastins of different species.

scholarly journals Vertical Point Sampling with a Camera

2011 ◽  
Vol 28 (2) ◽  
pp. 61-65 ◽  
Author(s):  
Mark J. Ducey ◽  
John A. Kershaw
Keyword(s):  
Basal Area ◽  
Stand Density ◽  
Double Sampling ◽  
Point Sampling ◽  
Field Techniques ◽  
Potential Applications ◽  
Stand Density Index ◽  
Detectable Bias ◽  
Horizontal Point Sampling

Abstract Vertical point sampling has seen relatively little use in practical forestry, in part because existing field techniques are difficult. We show how vertical point sampling can be implemented quickly and easily using a camera. We give tables and equations for calculating the height-squared factor, which plays a role similar to that of the basal area factor in horizontal point sampling. Some suggestions for choosing a height-squared factor are discussed, along with potential applications for further exploration. We illustrate the technique using a case study in southern Maine. Direct estimates with no statistically detectable bias were obtained using height-squared factors greater than 3. The results also suggested that the technique could be used as a correlate in double sampling for variables such as cubic volume, stand density index, and biomass, and possibly board foot volume as well.

scholarly journals An Evaluation of Big Basal Area Factor Sampling in Appalachian Hardwoods

2006 ◽  
Vol 23 (1) ◽  
pp. 62-65 ◽  
Author(s):  
John R. Brooks
Keyword(s):  
Data Collection ◽  
West Virginia ◽  
Sampling Error ◽  
Basal Area ◽  
Volume Estimation ◽  
Hardwood Forest ◽  
Standard Errors ◽  
Sampling Techniques ◽  
Appalachian Hardwoods

Abstract Big basal area factor (BAF) sampling techniques were investigated in a 70-year-old even-aged hardwood forest in northern West Virginia. Data collection procedures permitted the investigation of several small BAFs when employed with 12 big BAFs ranging from 55 to 300. Mean board foot volume per acre for sawtimber products was investigated along with a comparison of the resultant standard errors. The estimated mean volume per acre was quite stable. The same approximate mean volume per acre was obtained using big BAF values of 55 and 150 but with a 66% reduction in the number of sample trees needed for volume estimation. Sampling error increased with increasing big BAF, especially above values of 150. Sampling error within a single big BAF value was stable across the range of small BAFs sampled.

Post-stratified estimation: within-strata and total sample size recommendations

2011 ◽  
Vol 41 (5) ◽  
pp. 1130-1139 ◽  
Author(s):  
James A. Westfall ◽  
Paul L. Patterson ◽  
John W. Coulston
Keyword(s):  
Sample Size ◽  
Forest Inventory ◽  
Total Sample ◽  
Standard Errors ◽  
Sample Sizes ◽  
Total Sample Size ◽  
Survey Statistics ◽  
Population Structures ◽  
The Mean ◽  
Volume Estimates

Post-stratification is used to reduce the variance of estimates of the mean. Because the stratification is not fixed in advance, within-strata sample sizes can be quite small. The survey statistics literature provides some guidance on minimum within-strata sample sizes; however, the recommendations and justifications are inconsistent and apply broadly for many different population structures. The impacts of minimum within-strata and total sample sizes on estimates of means and standard errors were examined for two forest inventory variables: proportion forestland and cubic net volume. Estimates of the means seem unbiased across a range of minimum within-strata sample sizes. A ratio that described the decrease in variability with increasing sample size allowed for assessment of minimum within-strata sample requirements to obtain stable estimates of means. This metric indicated that the minimum within-strata sample size should be at least 10. Estimates of standard errors were found to be biased at small total sample sizes. To obtain a bias of less than 3%, the required minimum total sample size was 25 for proportion forestland and 75 for cubic net volume. The results presented allow analysts to determine within-stratum and total sample size requirements corresponding to their criteria for acceptable levels of bias and variability.

Is BAF 10 a Good Choice for Point Sampling?

1984 ◽  
Vol 1 (2) ◽  
pp. 23-24 ◽  
Author(s):  
Harry V. Wiant ◽  
David O. Yandle ◽  
Richard Andreas
Keyword(s):  
Basal Area ◽  
Good Choice ◽  
Hardwood Forest ◽  
Mean Square ◽  
Point Sampling ◽  
Volume Estimates ◽  
Mean Square Errors

Abstract The use of basal-area-factor (BAF)-5 and BAF-10 when point sampling in an Appalachian hardwood forest caused serious underestimation of sawtimber volume BAF's of 20 and 40 gave appropriate volume estimates and smallest mean-square errors. We recommend that BAF's 20 to 40 be used for sawtimber cruises. North. J. Appl. For. 2:23-24, June 1984.

scholarly journals Quick Volume Coefficient Determination for Point Sampling

2007 ◽  
Vol 24 (4) ◽  
pp. 314-316
Author(s):  
Christopher Dahl ◽  
Brent Harding ◽  
Harry Wiant
Keyword(s):  
Constant Coefficient ◽  
Point Sampling ◽  
Local Coefficients ◽  
Central Pennsylvania ◽  
Volume Coefficient ◽  
Species Specific ◽  
Volume Estimates

Abstract Grosenbaugh developed a formula for making quick point-sample estimates of sawtimber volume without measuring diameter. Local coefficients were created for a study area in central Pennsylvania hardwoods and were compared with volume estimates using a range of previously published coefficients. Results indicate that a general constant coefficient of 66 produces sawtimber volume estimates that are as good as using species-specific local coefficients for Pennsylvania hardwoods.

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