A fixed count sampling estimator of stem density based on a survival function
In fixed count sampling (FCS) a fixed number (k) of observations is made at n randomly selected sample locations. For estimation of stem density, the distance from a random sample location to the k nearest trees was measured. It is known that practical FCS estimators of stem density are biased. With...
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| Format: | Article |
| Language: | English |
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Czech Academy of Agricultural Sciences
2015-11-01
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| Series: | Journal of Forest Science |
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| Online Access: | https://jfs.agriculturejournals.cz/artkey/jfs-201511-0003_a-fixed-count-sampling-estimator-of-stem-density-based-on-a-survival-function.php |
| _version_ | 1797898776631836672 |
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| author | S. Magnussen |
| author_facet | S. Magnussen |
| author_sort | S. Magnussen |
| collection | DOAJ |
| description | In fixed count sampling (FCS) a fixed number (k) of observations is made at n randomly selected sample locations. For estimation of stem density, the distance from a random sample location to the k nearest trees was measured. It is known that practical FCS estimators of stem density are biased. With the objective of reducing bias in FCS estimators of stem density, a new estimator derived from a survival function with distance acting as time was presented. To allow for spatial heterogeneity in stem density, the survival function includes shared frailty. Encouraging results with k = 6 in terms of bias, root mean squared error (RMSE), and coverage of nominal 95% confidence intervals were obtained in an extensive testing with simulated random sampling from 54 actual and four simulated spatial point patterns of tree locations. Sample sizes were 9, 15, and 30, with 1200 replications per setting. The performance across sites of the new FCS estimator was variable but almost paralleled that of a design-based estimator with fixed area plots. Users of the new FCS estimator can expect an absolute relative bias and a root mean squared error that are 1% greater than for sampling with fixed area plots holding an average of k trees. The chance of a smaller RMSE with the proposed estimator was estimated at 0.44. |
| first_indexed | 2024-04-10T08:18:29Z |
| format | Article |
| id | doaj.art-73281107680b49a8bb3d9249d0a81dcb |
| institution | Directory Open Access Journal |
| issn | 1212-4834 1805-935X |
| language | English |
| last_indexed | 2024-04-10T08:18:29Z |
| publishDate | 2015-11-01 |
| publisher | Czech Academy of Agricultural Sciences |
| record_format | Article |
| series | Journal of Forest Science |
| spelling | doaj.art-73281107680b49a8bb3d9249d0a81dcb2023-02-23T03:42:38ZengCzech Academy of Agricultural SciencesJournal of Forest Science1212-48341805-935X2015-11-01611148549510.17221/46/2015-JFSjfs-201511-0003A fixed count sampling estimator of stem density based on a survival functionS. Magnussen0Natural Resources Canada, Canadian Forest Service, Victoria BC, CanadaIn fixed count sampling (FCS) a fixed number (k) of observations is made at n randomly selected sample locations. For estimation of stem density, the distance from a random sample location to the k nearest trees was measured. It is known that practical FCS estimators of stem density are biased. With the objective of reducing bias in FCS estimators of stem density, a new estimator derived from a survival function with distance acting as time was presented. To allow for spatial heterogeneity in stem density, the survival function includes shared frailty. Encouraging results with k = 6 in terms of bias, root mean squared error (RMSE), and coverage of nominal 95% confidence intervals were obtained in an extensive testing with simulated random sampling from 54 actual and four simulated spatial point patterns of tree locations. Sample sizes were 9, 15, and 30, with 1200 replications per setting. The performance across sites of the new FCS estimator was variable but almost paralleled that of a design-based estimator with fixed area plots. Users of the new FCS estimator can expect an absolute relative bias and a root mean squared error that are 1% greater than for sampling with fixed area plots holding an average of k trees. The chance of a smaller RMSE with the proposed estimator was estimated at 0.44.https://jfs.agriculturejournals.cz/artkey/jfs-201511-0003_a-fixed-count-sampling-estimator-of-stem-density-based-on-a-survival-function.phpbiascoverageforest inventoryspatial point patternstandard errorroot mean squared error |
| spellingShingle | S. Magnussen A fixed count sampling estimator of stem density based on a survival function Journal of Forest Science bias coverage forest inventory spatial point pattern standard error root mean squared error |
| title | A fixed count sampling estimator of stem density based on a survival function |
| title_full | A fixed count sampling estimator of stem density based on a survival function |
| title_fullStr | A fixed count sampling estimator of stem density based on a survival function |
| title_full_unstemmed | A fixed count sampling estimator of stem density based on a survival function |
| title_short | A fixed count sampling estimator of stem density based on a survival function |
| title_sort | fixed count sampling estimator of stem density based on a survival function |
| topic | bias coverage forest inventory spatial point pattern standard error root mean squared error |
| url | https://jfs.agriculturejournals.cz/artkey/jfs-201511-0003_a-fixed-count-sampling-estimator-of-stem-density-based-on-a-survival-function.php |
| work_keys_str_mv | AT smagnussen afixedcountsamplingestimatorofstemdensitybasedonasurvivalfunction AT smagnussen fixedcountsamplingestimatorofstemdensitybasedonasurvivalfunction |