Data Reference
SCI Survey Description
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Overall Objective
The overall objective of this plan is to annually estimate the average total costs, food (in 10 main traits), very food (in 10 general traits) and income of households, as well as to annually estimate the changes in these averages at the national urban areas level and to annually estimate the average total costs, food, non-food and income of households at the urban areas level of each of the provinces.
Target Population
The target population includes all normal resident and group households in the urban areas of the country. Non-resident normal households and institutional households are excluded from this plan.
Statistical Unit
The statistical unit is a normal resident or group household in the country.
Reference Period
The reference period for different questions is, depending on the case, the past week, the past month, and the past 12 months.
Data Collection Period
The data collection period of this plan is from April 1 of the relevant year until the end of March of the following year.
Data Gathering Method
The required information is collected through face-to-face interviews with sample households and completion of questionnaires.
Sampling Framework
The first stage sampling framework in this plan is the fourth baseline sample of household surveys that includes the first stage sampling units (clusters). Each cluster includes one block, part of a large block, or in some cases a set of several small blocks that are constructed based on information from the general population and housing census so that it includes at least 350 households.
The second stage sampling framework is a list of names and addresses of resident ordinary households and some groups in selected sample clusters from the baseline sample.
Sampling Method
The samples in this plan are selected in three stages using probabilistic sampling methods. In the first stage, the sampling clusters of each stratum of the baseline sample are randomly selected using simple random sampling. In the second stage, in each sample cluster, six-household rotation groups are constructed and three rotation groups are determined for the survey in each year based on the rotation pattern. In the third stage, inside each of the rotation groups, two households are randomly selected as the main sample households and the remaining four households in the rotation group are considered as substitute households.
In addition to estimating parameter levels (estimating parameters at a specific point in time) in this plan, estimating changes is also of interest. To obtain both types of level and change estimates for parameters with acceptable accuracy, rotational sampling is used. Rotational sampling, by keeping part of the sample units fixed between two survey periods and changing the rest, provides the possibility to estimate both levels and changes of parameters. Optimal implementation of rotational sampling requires the use of a baseline sample.
The rotational pattern selected for this plan is the three in then out pattern, according to which during three years from each rotation group, which is equivalent to 2 sample households, at most 3 surveys are conducted. This means that a household, depending on the rotation group it belongs to, is included in the sample for a maximum of 3 years and after that it is permanently excluded from the sample. Every year, inside each cluster, surveys are conducted from three rotation groups (equivalent to 6 households) as follows:
- The group that has entered the sample for the first time
- The group that has been placed in the sample for the second time
- The group that has been placed in the sample for the third time
Thus, the overlap between two years \(t\) and \(t+i\) is:
Every year, surveys are conducted from three rotation groups inside each cluster. The rotation pattern used in this plan is presented in the tables below:
| rotation group | 1389 | 1390 | 1391 |
|---|---|---|---|
| A | A1 | - | - |
| B | B1 | B2 | - |
| C | C1 | C2 | C3 |
| D | - | D1 | D2 |
| E | - | - | E1 |
| rotation group | 1392 | 1393 | 1394 | 1395 | 1396 |
|---|---|---|---|---|---|
| A | A1 | - | - | - | - |
| B | B1 | B1 | - | - | - |
| C | C1 | C2 | C3 | - | - |
| D | - | D1 | D2 | D3 | - |
| E | - | - | E1 | E2 | E3 |
| F | - | - | - | F1 | F2 |
| G | - | - | - | - | G1 |
| rotation group | 1397 | 1398 | 1399 | 1400 | 1401 | 1402 | 1403 | 1404 | 1405 | 1406 |
|---|---|---|---|---|---|---|---|---|---|---|
| A | A1 | - | - | - | - | - | - | - | - | - |
| B | B1 | B2 | - | - | - | - | - | - | - | - |
| C | C1 | C2 | C3 | - | - | - | - | - | - | - |
| D | - | D1 | D2 | D3 | - | - | - | - | - | - |
| E | - | - | E1 | E2 | E3 | - | - | - | - | - |
| F | - | - | - | F1 | F2 | F3 | - | - | - | - |
| G | - | - | - | - | G1 | G2 | G3 | - | - | - |
| H | - | - | - | - | - | H1 | H2 | H3 | - | - |
| I | - | - | - | - | - | - | I1 | I2 | I3 | - |
| J | - | - | - | - | - | - | - | J1 | J2 | J3 |
| K | - | - | - | - | - | - | - | - | K1 | K2 |
| L | - | - | - | - | - | - | - | - | - | L1 |