Selection from the list of topics

Estimates and standard error of the estimates

The results published in the NFI tables are estimates for variables in the Swiss forest (population parameters) whose true values are not known and must therefore be extrapolated (estimated) from the NFI sample data.

The extrapolations carry uncertainties. However, the accuracy of the extrapolations can be reliably estimated from the NFI sample, which is designed to be a random sample. To this end, all NFI tables include a second figure in addition to the estimate itself, namely the standard error of the estimate.

In most tables the percent standard error is reported (±%), but the absolute standard error (±) is also reported occasionally, especially for estimated percentages. The relationship between absolute and percent standard error is as follows:

percent standard error = absolute standard error / estimate × 100

absolute standard error = percent standard error × estimate / 100

Information on the forest road network is based on a full survey of all forest roads. In this case, there is no need to specify a standard error because there is no uncertainty caused by sampling.

Confidence interval of the estimate

With the estimate and the standard error of the estimate, the limits of the so-called confidence interval of the estimate can be calculated as:

lower limit = estimate – tQ × absolute standard error

upper limit = estimate + tQ × absolute standard error

If the simple standard error is used for the calculation (tQ = 1), then the 68% confidence interval is formed. In this case, the true value of the population parameter has a 68% probability of lying within this confidence interval of the estimate. If the double standard error is used (tQ = 2), then there is a 95% probability that the true value lies within this 95% confidence interval.

Significance of the estimate

The confidence interval can be used to statistically test whether the estimated population parameter is larger or smaller than a specific reference or target value, or whether two estimated population parameters truly differ (in the real population). For practical applications, proceed as follows: if a reference value lies outside the confidence interval, the estimated population value can be interpreted as being significantly different from it; if it lies within the confidence interval, the difference between the estimated population parameter and the reference value can be interpreted as random or not significant. When two population parameters are compared, they can be interpreted as differing significantly if their confidence intervals do not overlap.

Dealing with missing values

When calculating a results table, data are not always available for all combinations of characteristics^* of the classification variables and regional demarcation applied. In most cases, this indicates that the attribute estimated with the respective target variable does not occur or occurs only very rarely. Usually, the value 0 is used (imputed). However, as this value is not based on direct measurements, the associated standard error is represented with a full stop [.]. If the imputed value of 0 is referred to in the calculation, e.g. in the case of percentages or certain change estimates, no value can be entered. In this case, the estimated value and standard error are both represented with a full stop [.].

For example, no Arolla pines have been found and measured in the Swiss Plateau to date (growing stock of Arolla pines by production region). The values can be assumed to be missing because Arolla pine does not occur in the Swiss Plateau and therefore the growing stock there must be 0.

^* e.g. ‘Arolla pine’ characteristic of the classification variable ‘tree species’ and ‘Swiss plateau’ characteristic of the ‘regional demarcation’

Changes

There are two types of changes in the NFI:

The first type involves specific target variables relating to components of change, such as increment, fellings, mortality and losses. These target variables are only available for two consecutive inventory cycles, e.g. NFI3–NFI4. In the evaluation of components of change, the classification variable characteristic of the second inventory cycle is assigned to the first inventory cycle. These evaluations therefore do not take into account potential changes in a classification variable characteristic from the earlier to the later inventory (e.g. from private to public ownership).

With the second type of change, the difference in target variables, such as number of stems, growing stock or forest area, is used to assess the change between two inventory cycles. Target variables are generally used to represent states, such as that in NFI4, but can also indicate the net change between any two inventory cycles, e.g. NFI1–NFI4. In evaluations of change using these target variables, the change in a classification variable characteristic is considered in the analysis. Consequently, one can detect, for example, that the forest area without shrub forest increased between the two inventory cycles. This only has an effect on classification variables whose characteristic (class) can actually change, e.g. the affiliation with a forest area or the tree condition.

NFI5
volume of bolewood (HG 2010)
type of assortment · tree species (5 classes)
regional demarcation: canton
unit: 1000 m³
evaluation area: accessible forest without shrub forest NFI1-NFI5
grid: 1.4 km grid, subgrids 1-5
state 2018/26
		canton
		AG		AI		AR		BE		BL/BS		FR		GE		GL		GR		JU		LU		NE		NW		OW		SG		SH		SO		SZ		TG		TI		UR		VD		VS		ZG		ZH		Switzerland
type of assortment	tree species (5 classes)	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%	1000 m³	±%
n/a	n/a	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	spruce	0	0	0	0	0	0	0	0	0	0	0	0	0	.	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	fir	0	0	0	0	0	0	0	0	0	0	0	0	0	.	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	other conifers	0	0	0	.	0	0	0	0	0	0	0	0	0	0	0	.	0	0	0	0	0	0	0	0	0	.	0	0	0	0	0	0	0	0	0	.	0	0	0	0	0	.	0	0	0	0	0	0	0	0	0	0
	beech	0	0	0	0	0	0	0	0	0	0	0	0	0	.	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	other broadleaves	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	indeterminable	0	0	0	.	0	0	0	0	0	0	0	0	0	.	0	0	0	0	0	.	0	0	0	.	0	.	0	0	0	0	0	.	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	.	0	0	0	0
	total	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
coniferous wood	n/a	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	spruce	0	.	0	.	10	100	32	100	0	.	232	94	0	.	0	.	198	96	0	.	0	.	0	.	10	100	0	.	375	56	0	.	0	.	0	.	17	100	0	.	0	.	0	.	186	72	0	.	0	.	1059	36
	fir	0	.	0	.	0	.	46	100	0	.	130	100	0	.	0	.	0	.	0	.	0	.	0	.	18	100	0	.	42	100	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	236	61
	other conifers	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	84	73	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	19	100	0	.	0	.	0	.	74	83	0	.	0	.	177	50
	beech	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	other broadleaves	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	indeterminable	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	total	0	.	0	.	10	100	78	100	0	.	362	72	0	.	0	.	282	71	0	.	0	.	0	.	28	100	0	.	417	52	0	.	0	.	0	.	36	100	0	.	0	.	0	.	260	71	0	.	0	.	1473	30
coniferous shortwood	n/a	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	spruce	2021	21	1897	34	1590	31	20836	8	376	43	4608	17	1	100	3111	24	27066	7	68	85	5890	14	23	100	1050	43	2814	22	6883	15	988	30	1176	24	4859	17	1759	23	5954	21	3706	21	6234	14	10821	10	637	40	4447	15	118813	3
	fir	1004	30	376	41	1097	39	10199	10	198	40	1438	29	0	.	432	48	1699	23	166	67	4448	16	226	100	265	58	676	31	2280	20	128	69	983	24	1775	25	960	34	1104	30	929	32	3111	19	718	35	243	42	1582	21	36037	5
	other conifers	541	28	0	.	10	74	1230	23	517	55	30	72	72	100	25	92	8661	9	26	100	288	45	0	.	4	100	224	75	530	66	344	42	355	28	108	67	379	38	2809	15	198	57	204	36	8598	10	28	100	991	20	26172	5
	beech	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	other broadleaves	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	indeterminable	0	.	0	.	0	0	0	0	0	.	0	0	0	.	0	.	0	0	0	.	0	0	0	.	0	0	0	0	0	0	0	.	0	.	0	.	0	.	0	.	0	0	0	0	0	0	0	.	0	0	0	0
	total	3565	17	2273	32	2697	28	32265	7	1090	32	6076	16	73	100	3569	22	37425	6	260	65	10626	12	249	100	1319	37	3714	20	9693	13	1461	26	2514	17	6742	15	3098	19	9867	14	4833	19	9549	13	20137	8	909	35	7020	13	181022	2
coniferous mediumwood	n/a	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	spruce	11	100	0	.	0	.	1271	26	181	68	468	56	0	.	0	.	421	46	259	55	653	38	61	76	362	71	608	55	985	39	60	100	68	59	0	.	198	74	212	61	0	.	356	59	1839	25	0	.	271	55	8283	12
	fir	124	100	0	.	0	.	1721	27	174	52	0	.	0	.	0	.	123	65	66	73	1134	29	65	100	27	100	233	59	313	47	0	.	116	46	0	.	34	100	23	100	0	.	346	41	616	43	0	.	86	67	5199	13
	other conifers	0	.	0	.	0	.	173	43	11	100	41	82	0	.	0	.	297	55	58	100	34	100	83	71	0	.	0	.	80	71	38	77	53	60	0	.	0	.	285	51	0	.	96	55	414	39	0	.	40	82	1702	18
	beech	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	other broadleaves	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	indeterminable	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	0	0	.	0	0	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	0	0	.	0	.	0	0
	total	135	92	0	.	0	.	3165	22	366	53	509	52	0	.	0	.	840	40	382	47	1822	29	208	54	389	71	840	51	1378	35	97	77	238	43	0	.	232	71	519	43	0	.	797	37	2869	23	0	.	397	42	15183	10
coniferous longwood	n/a	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	spruce	392	63	349	72	342	68	2724	18	133	87	1695	30	2	100	0	.	99	100	1880	25	52	100	3900	15	0	.	185	100	630	54	312	70	287	94	0	.	506	47	0	.	0	.	4095	16	663	55	0	.	531	47	18778	8
	fir	299	60	113	100	237	89	2353	18	145	99	715	39	3	100	0	.	0	.	3329	20	51	100	3400	17	0	.	295	100	435	51	28	100	102	72	0	.	167	61	0	.	0	.	2705	17	104	91	0	.	107	52	14587	8
	other conifers	0	.	0	.	0	.	534	53	27	71	295	58	12	100	0	.	12	100	235	41	187	100	70	72	0	.	0	.	0	.	7	100	0	.	0	.	14	100	0	.	0	.	356	37	16	75	0	.	13	100	1779	23
	beech	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	other broadleaves	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	indeterminable	0	.	0	.	0	.	0	0	0	.	0	.	0	.	0	.	0	.	0	0	0	.	0	0	0	.	0	.	0	0	0	.	0	.	0	.	0	.	0	.	0	.	0	0	0	.	0	.	0	.	0	0
	total	691	50	462	71	579	61	5611	15	305	89	2706	25	17	77	0	.	110	100	5444	17	290	100	7370	12	0	.	480	100	1065	42	346	65	389	73	0	.	688	43	0	.	0	.	7155	13	783	49	0	.	651	45	35143	6
broadleaf roundwood	n/a	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	spruce	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	fir	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	other conifers	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	beech	4299	15	274	47	424	34	11912	8	2212	20	2874	19	0	.	869	29	1636	23	2900	17	3337	17	1216	18	441	42	1281	30	5030	15	1878	21	4004	15	1573	25	1538	20	4711	12	905	35	6128	12	890	29	299	44	3833	13	64463	3
	other broadleaves	2296	16	16	72	527	34	4670	10	972	22	1967	20	328	57	784	33	2473	16	2001	22	1374	26	696	22	658	48	252	46	3105	15	441	28	1447	18	898	30	2250	22	9150	8	455	33	4116	14	1635	15	179	48	3192	13	45881	3
	indeterminable	0	.	0	.	1	100	1	71	12	93	0	.	0	.	0	.	13	100	1	100	1	100	0	.	0	.	1	100	2	100	0	.	4	100	0	.	1	100	4	58	0	.	24	61	0	.	0	.	5	100	70	34
	total	6595	13	289	47	952	30	16584	7	3196	18	4841	16	328	57	1653	24	4122	14	4902	14	4712	15	1911	15	1100	35	1534	27	8137	13	2319	20	5455	13	2471	22	3789	17	13866	6	1361	30	10268	10	2525	15	478	43	7030	11	110414	2
total	n/a	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.
	spruce	2423	20	2245	31	1941	28	24864	7	689	34	7003	14	3	75	3111	24	27783	6	2206	22	6595	13	3984	15	1422	36	3607	20	8874	13	1360	27	1531	26	4859	17	2480	20	6166	20	3706	21	10684	10	13509	9	637	40	5248	14	146933	2
	fir	1427	26	489	39	1334	36	14318	8	516	36	2283	22	3	100	432	48	1821	22	3561	19	5634	14	3691	17	310	51	1203	32	3069	17	156	59	1202	21	1775	25	1161	30	1126	29	929	32	6162	12	1437	26	243	42	1775	19	56058	4
	other conifers	541	28	0	.	10	74	1936	21	555	52	367	48	84	87	25	92	9053	9	320	36	509	45	153	50	4	100	224	75	610	58	389	38	407	26	108	67	413	35	3093	14	198	57	655	24	9102	9	28	100	1044	19	29830	5
	beech	4299	15	274	47	424	34	11912	8	2212	20	2874	19	0	.	869	29	1636	23	2900	17	3337	17	1216	18	441	42	1281	30	5030	15	1878	21	4004	15	1573	25	1538	20	4711	12	905	35	6128	12	890	29	299	44	3833	13	64463	3
	other broadleaves	2296	16	16	72	527	34	4670	10	972	22	1967	20	328	57	784	33	2473	16	2001	22	1374	26	696	22	658	48	252	46	3105	15	441	28	1447	18	898	30	2250	22	9150	8	455	33	4116	14	1635	15	179	48	3192	13	45881	3
	indeterminable	0	0	0	.	1	100	1	71	12	93	0	0	0	.	0	0	13	100	1	100	1	100	0	0	0	0	1	100	2	100	0	.	4	100	0	0	1	100	4	58	0	0	24	61	0	0	0	.	5	100	70	34
	total	10986	11	3024	29	4237	23	57702	5	4956	17	14494	11	418	54	5221	19	42780	5	10989	12	17449	10	9739	11	2835	26	6568	17	20690	10	4223	18	8595	12	9213	14	7842	14	24252	7	6194	17	27770	7	26574	7	1387	32	15097	9	343236	1

Table citation

Abegg, M.; Ahles, P.; Allgaier Leuch, B.; Cioldi, F.; Didion, M.; Düggelin, C.; Fischer, C.; Herold, A.; Meile, R.; Rohner, B.; Rösler, E.; Speich, S.; Temperli, C.; Traub, B.,
2023: Swiss national forest inventory - Result table No. 1403843. Birmensdorf, Swiss Federal Research Institute WSL

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