2. METHODOLOGY of the SAMPLE to Conduct the Survey, a Multi-Level
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2. METHODOLOGY OF THE SAMPLE To conduct the survey, a multi-level proportional probability sample has been designed. Based on the 11 regional (marz) administrative and territorial division of RA, the sample design algorithm forms the preliminary sampling units (PSU) from the general population through the stratification method. The preliminary sampling units in marzes have been chosen by the following way: • PSU comprised 12 for Yerevan city, based on the number of district communities, • for those towns, which have more than 20000 population, separate preliminary sampling units were chosen in each marz, • small towns in each marz were grouped in one preliminary sampling unit, which was called “urban area”, • all villages in each marz were grouped in one preliminary sampling unit, which was called “rural area”. Thus, the total number of preliminary sampling units comprised 48. At the first stage of sampling the total volume of the sampling was divided into preliminary units by the proportion of the square root of the number of those households, which were involved in the given preliminary sampling units. 2001 Armenian population census results were used to calculate the mentioned proportions. Method of the proportion by using the square root was selected, as it, unlike the traditional PPS algorithm, enables to derive unbiased estimates of statistical indicators bringing to insignificant increase in variances within the preliminary sampling units on one hand, and on the other hand this approach increases the probability to select the settlements with a small number of households. As a result of the above-mentioned algorithm, the following distribution of the sampling volume was derived: PSU Marz Name Household Square % Selected root household 1 YEREVAN Adjapnyak district 26851 163.9 2.83 72 2 Avan district 12333 111.1 1.92 49 3 Arabkir district 36369 190.7 3.30 84 4 Davitashen district 10063 100.3 1.73 44 5 Erebuni district 26776 163.6 2.83 72 6 Kentron district 34056 184.5 3.19 81 7 Malatia-Sebastia district 33137 182.0 3.15 80 8 Nor Nork district 36525 191.1 3.30 84 9 Nork-Marash district 2502 50.0 0.86 22 10 Nubarashen district 2020 44.9 0.78 20 11 Shengavit district 34517 185.8 3.21 82 12 Qanaqer-Zeytun district 20812 144.3 2.49 63 13 ARAGATSOTN Urban Area 3485 59.0 1.02 26 14 Rural Area 26377 162.4 2.81 71 15 Ashtarak town 5558 74.6 1.29 33 5 PSU Marz Name Household Square % Selected root household 16 ARARAT Urban Area 2825 53.2 0.92 23 17 Rural Area 44780 211.6 3.66 93 18 Artashat town 7489 86.5 1.50 38 19 Ararat town 4330 65.8 1.14 29 20 Masis town 4846 69.6 1.20 31 21 ARMAVIR Urban Area 3019 54.9 0.95 24 22 Rural Area 39260 198.1 3.43 87 23 Armavir town 8330 91.3 1.58 40 24 Vagharshapat town 13038 114.2 1.97 50 25 GEGHARKUNIK Urban Area 7894 88.8 1.54 39 26 Rural Area 33968 184.3 3.19 81 27 Gavar (Kamo) town 7041 83.9 1.45 37 28 Sevan town 6354 79.7 1.38 35 29 LORI Urban Area 19621 140.1 2.42 61 30 Rural Area 33018 181.7 3.14 80 31 Vanadzor town 33804 183.9 3.18 81 32 KOTAYK Urban Area 8141 90.2 1.56 40 33 Rural Area 27000 164.3 2.84 72 34 Hrazdan town 14623 120.9 2.09 53 35 Abovyan town 13626 116.7 2.02 51 36 Charentsavan town 7551 86.9 1.50 38 37 SHIRAK Urban Area 6373 79.8 1.38 35 38 Rural Area 28046 167.5 2.90 74 39 Gyumri town 40823 202.0 3.49 89 40 SYUNIK Urban Area 8249 90.8 1.57 40 41 Rural Area 12148 110.2 1.91 48 42 Kapan town 11646 107.9 1.87 47 43 Goris town 5102 71.4 1.24 31 44 VAYOTS DZOR Urban Area 5746 75.8 1.31 33 45 Rural Area 8529 92.4 1.60 41 46 TAVUSH Urban Area 8522 92.3 1.60 41 47 Rural Area 21432 146.4 2.53 64 48 Idjevan town 5103 71.4 1.24 31 813658 5783.1 100.0 2539 At the second stage of sampling preliminary sampling units corresponding to Yerevan city and the large cities were included in the sampling by the probability of 1, in the other units, settlements were selected through the random sampling method – by the proportional probability of the number of households in the given settlement. At the third stage of sampling clusters appropriate to the territorial units were selected from the “urban areas”, which had been used during the population census. The sample of clusters was designed according to the PPS algorithm. Thus, at the second and third stages of the sample, the self-weighting of households in the preliminary sampling units was ensured. Households' addresses were selected using the systematic selection method. 6.