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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
growing stock (stemwood)
altitudinal vegetation belts (NaiS; 6 classes) · ownership (2 categories)
regional demarcation: canton
unit: 1000 m³
evaluation area: accessible forest without shrub forest NFI4/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
altitudinal vegetation belts (NaiS; 6 classes)	ownership (2 categories)	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	.
	public	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	.
	private	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	.
upper subalpine	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	.
	public	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	4666	14	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	640	33	0	.	0	.	2012	23	0	.	0	.	7318	11
	private	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	188	51	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	399	43	0	.	0	.	587	34
	total	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	4854	14	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	640	33	0	.	0	.	2411	20	0	.	0	.	7906	11
subalpine	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	.
	public	0	.	0	.	0	.	598	55	0	.	166	100	0	.	595	51	13720	11	0	.	0	.	0	.	0	.	986	48	895	49	0	.	0	.	366	68	0	.	3617	18	391	57	691	39	8028	14	0	.	0	.	30052	7
	private	0	.	0	.	0	.	4826	19	0	.	0	.	0	.	0	.	2915	23	0	.	20	100	0	.	454	60	94	100	1	100	0	.	0	.	0	.	0	.	201	100	329	74	134	77	1873	39	0	.	0	.	10846	13
	total	0	.	0	.	0	.	5424	18	0	.	166	100	0	.	595	51	16634	10	0	.	20	100	0	.	454	60	1081	45	895	48	0	.	0	.	366	68	0	.	3818	18	720	46	825	35	9901	13	0	.	0	.	40899	6
high-montane	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	.
	public	0	.	0	.	0	.	1493	41	0	.	1011	42	0	.	1085	52	20500	9	0	.	319	70	0	.	45	100	1762	33	835	47	0	.	0	.	1033	36	0	.	5938	16	1967	32	2579	30	11232	12	0	0	0	.	49798	6
	private	0	.	0	.	0	.	6377	17	0	.	1181	44	0	.	0	.	6297	19	0	.	499	54	3	100	64	100	193	100	311	67	0	.	0	.	312	71	0	.	115	100	666	72	1582	42	4562	20	0	.	0	.	22163	9
	total	0	.	0	.	0	.	7870	16	0	.	2192	31	0	.	1085	52	26797	8	0	.	818	43	3	100	109	72	1955	31	1146	39	0	.	0	.	1345	32	0	.	6054	16	2633	30	4161	24	15793	10	0	0	0	.	71961	5
lower and upper montane	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	.
	public	1116	37	1628	41	2267	36	16412	10	1780	33	6535	18	0	.	3094	25	6208	16	6221	18	3327	25	5371	18	1503	43	2664	25	8995	16	1225	37	4757	18	6651	18	154	75	8526	18	1624	31	15182	10	1950	28	1059	38	2552	25	110803	4
	private	389	67	2123	39	2483	33	22378	10	354	62	4284	22	0	.	916	41	897	41	2477	29	9476	15	4972	19	1272	40	1466	50	12147	15	156	100	1181	42	2034	32	1943	31	1564	31	1229	44	4599	21	1284	39	678	63	5871	19	86172	4
	total	1505	33	3751	28	4750	24	38790	7	2134	29	10820	14	0	.	4009	21	7105	15	8698	15	12802	12	10343	12	2775	29	4130	24	21142	10	1381	34	5937	16	8685	15	2098	29	10090	16	2854	26	19781	9	3234	23	1737	33	8423	15	196975	2
submontane	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	.
	public	7697	13	0	.	0	.	7531	14	2336	24	1868	31	0	.	0	.	678	42	2099	32	1749	32	1012	39	0	.	312	70	927	41	2581	25	2730	22	345	71	3206	23	0	.	346	77	3483	19	332	47	158	100	5188	15	44578	5
	private	2925	26	0	.	0	.	7734	15	1173	38	2123	32	0	.	0	.	152	81	1166	39	3930	23	39	100	0	.	0	.	831	50	781	46	1060	43	334	78	3570	22	0	.	731	61	3829	22	120	100	142	100	3534	21	34177	7
	total	10622	12	0	.	0	.	15266	10	3509	20	3991	22	0	.	0	.	829	37	3265	24	5679	18	1050	38	0	.	312	70	1759	32	3362	22	3790	20	679	53	6777	16	0	.	1078	48	7313	15	452	43	300	71	8722	12	78755	4
hyperinsubric and colline	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	.
	public	0	.	0	.	0	.	0	.	0	.	0	.	162	80	0	.	812	39	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	3978	15	0	.	165	71	624	32	0	.	24	100	5764	12
	private	0	.	0	.	0	.	0	.	0	.	0	.	323	71	0	.	249	71	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	86	100	6494	13	0	.	71	100	507	46	0	.	60	100	7790	12
	total	0	.	0	.	0	.	0	.	0	.	0	.	485	54	0	.	1061	34	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	0	.	86	100	10472	9	0	.	236	58	1132	27	0	.	83	77	13555	7
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	.
	public	8813	12	1628	41	2267	36	26034	8	4116	19	9580	14	162	80	4774	21	46582	5	8320	15	5394	19	6383	16	1548	42	5724	18	11653	13	3806	21	7486	14	8395	15	3361	22	22699	8	4329	20	22100	8	24179	8	1217	35	7763	13	248314	2
	private	3315	24	2123	39	2483	33	41315	7	1527	33	7588	17	323	71	916	41	10698	13	3643	23	13925	12	5013	19	1790	32	1754	44	13290	14	937	42	2241	30	2680	28	5599	18	8375	12	2956	30	10216	14	8745	15	819	55	9465	14	161736	3
	total	12128	11	3751	28	4750	24	67349	5	5643	16	17168	11	485	54	5689	18	57280	5	11963	12	19319	10	11396	11	3339	26	7478	17	24943	9	4744	18	9727	12	11076	13	8960	13	31074	6	7284	17	32316	7	32923	7	2036	30	17228	9	410050	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. 1260016. Birmensdorf, Swiss Federal Research Institute WSL

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