ANNEX IISupplementary provisions
ANNEX II SAMPLE 1. The Statistical Business Register (SBR) referred to in Council Regulation (EEC) No 2186/93 ( 1 ) shall normally be taken as the main source of the sampling frame. A nationally representative stratified probability sample of enterprises shall be taken from this frame. 2. The sample shall be stratified by NACE and size category according to the following minimum specification: — 20 NACE rev1.1 categories (C, D (15-16, 17-19, 21-22, 23-26, 27-28, 29-33, 34-35, 20 + 36-37), E, F, G (50, 51, 52), H, I (60-63, 64), J (65-66, 67), K + O) — 3 enterprise size categories, according to their number of persons employed: (10-49) (50-249) (250 and more) 3. A sample size shall be calculated to assure a maximum half length of the 95 % confidence interval of 0,2 for the estimated parameters, which are a proportion of ‘training enterprises’ (after allowance for the non-response rate in the sample) for each of the 60 stratified elements identified above. 4. The following formula may be used in determining the sample size: n h = 1/[c 2 . te h + 1/N h ] / r h Where: n h = the number of sampling units in the stratum cell, h r h = the anticipated response rate in the stratum cell, h c = maximum length of half the confidence interval te h = the anticipated proportion of training enterprises in the stratum cell, h N h = the total number of enterprises (training and non-training) in the stratum cell, h ( 1 ) OJ L 196, 5.8.1993, p. 1 . Regulation as amended by Regulation (EC) No 1882/2003 of the European Parliament and of the Council ( OJ L 284, 31.10.2003, p. 1 ).