Forms survey weights (S.D. Langton).

### Options

`PRINT` = string token |
Controls printed output (`summary` , `stratumsummary` , `psusummary` ); default `summ` , `stra` , `psus` |
---|---|

`PLOT` = string token |
Controls which high-resolution graphs are plotted (`weights` ); default `*` i.e. none |

`STRATUMFACTOR` = factor |
Stratification factor; default `*` , i.e. unstratified |

`NUNITS` = tables, scalars or variates |
Numbers of units in each `STRATUMFACTOR` (for a multistage design these will be the number of primary sampling units) |

`SAMPLINGUNITS` = factor |
Factor indicating the primary sampling units; default `*` , i.e. single stage design. |

`NSECONDARYUNITS` = tables, scalars or variates |
Numbers of secondary sampling units for each level of the `SAMPLINGUNITS` factor |

### Parameters

`Y` = variates or scalars |
Response data or a scalar indicating the number of sampled units |
---|---|

`OUTWEIGHTS` = variates |
Saves weights |

### Description

`SVWEIGHT`

creates weights for surveys. The information about the numbers of sampling units in the survey population can be supplied in one of two ways.

1. The option `NUNITS`

can be used to list the number of primary sampling units per stratum using a table or variate with one value for each stratum. Similarly, in a two-stage design, `NSECONDARYUNITS`

indicates the number of secondary units in each primary sampling unit.

2. The dataset can contain the full survey population with unsampled (or non-responding) units indicated by missing values for the response variables (`Y`

parameter). This allows Genstat to deduce the numbers of units without the need to supply any further information; it is thus simple to use, but is not feasible with large or complex surveys. The `NUNITS`

(and `NSECONDARYUNITS`

if appropriate) option should be set to a value of -1 to indicate that this is required.

With the first method the `Y`

parameter can be left unset, except in the case of a simple random sample, where it must be set in order for the procedure to know the number of sampled units; in this case `Y`

can either be set to a variate containing the responses or to a scalar containing the number of sampled units. Other information on the survey design is provided using the `STRATUMFACTOR`

and `SAMPLINGUNITS`

options. The `OUTWEIGHTS`

parameter saves the variate of weights (corresponding to each response variable in the case where more than one `Y`

variable is set).

The `PRINT`

option allows you to print various summaries, and you can set `PLOT=weights`

to plot a histograms of the weights.

Options: `PRINT`

, `PLOT`

, `STRATUMFACTOR`

, `NUNITS`

, `SAMPLINGUNITS`

, `NSECONDARYUNITS`

.

Parameters: `Y`

, `OUTWEIGHTS`

.

### Method

The procedure uses the methods for survey analysis described in most survey analysis textbooks, calculating weights as the inverse of the probabilities of inclusion (see for example, Sarndal *et al*. 1992).

### Action with `RESTRICT`

Any restrictions on `Y`

, `SAMPLINGUNITS`

, `STRATUMFACTOR`

or `WEIGHTS`

are ignored.

### Reference

Sarndal, C., Swenssion, B. & Wretman, J. (1992). *Model Assisted Survey Sampling*. Springer-Verlag, New York.

### See also

Procedures: `SVBOOT`

, `SVCALIBRATE`

, `SVGLM`

, `SVHOTDECK`

, `SVREWEIGHT`

, `SVSAMPLE`

, `SVSTRATIFIED`

, `SVTABULATE`

.

Commands for: Survey analysis.

### Example

CAPTION 'SVWEIGHT example',!t(\ 'Orkney oats data (Sampford, Table 5.1, page 61).',\ 'Stratified analysis as Table 6.1, page 73'); STYLE=meta,plain VARIATE Oats READ Oats 15 20 18 18 23 27 25 60 28 128 69 72 : FACTOR [LEVELS=3; VALUES=4(1,2,3)] Stratum TABLE [CLASSIFICATION=Stratum; VALUES=12,12,11] N SVWEIGHT [PRINT=summary; STRATUM=Stratum; NUNITS=N] OUTWEIGHTS=weights CAPTION 'Check weights give correct total by comparing to SVSTRATIFIED result' PRINT SUM(weights*Oats);DECIMALS=2 SVSTRATIFIED [PRINT=totals; STRATUMFACTOR=Stratum] Oats; NUNITS=N CAPTION 'SVWEIGHT example 2',!t('Province 91 data',\ '(Lehtonen & Pahkinen, Table 3.7 & 3.8, page 88-9).');\ STYLE=meta,plain VARIATE UE91; DECIMALS=0 FACTOR CLU; DECIMALS=0 READ [SERIAL=yes] CLU,UE91 2 3 3 2 4 7 4 7 : 760 767 142 187 94 262 98 219 : VARIATE [VALUES=4(4)] nsu SVWEIGHT [PRINT=summary,psusummary; SAMPLINGUNITS=CLU; NUNITS=8; NS=nsu]\ OUTWEIGHTS=wt2stage PRINT SUM(wt2stage*UE91); DECIMALS=0 CAPTION 'SVWEIGHT example 3',!t('Province 91 data',\ '(Lehtonen and Pahkinen, Table 3.5 & 3.6, page 83-4),',\ 'using full population format.'); STYLE=meta,plain VARIATE UE91; DECIMALS=0 FACTOR CLU; DECIMALS=0 READ [SERIAL=yes] CLU,UE91 1 2 2 2 3 5 3 5 6 7 4 4 8 8 3 5 1 2 4 5 6 6 7 1 7 8 4 3 1 6 7 8 : * 666 528 760 * * * * * * * * 129 128 * * * 187 * * * * * * * 331 * * * * * 568 : SVWEIGHT [PRINT=summary,psusummary; SAMPLINGUNITS=CLU;\ NUNITS=-1; NSECONDARYUNITS=-1] UE91; OUTWEIGHTS=WGHT PRINT CLU,WGHT,UE91;DECIMALS=0 PRINT SUM(WGHT*UE91);DECIMALS=0