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Weighting respondents

This section describes the facilities for weighting data.  This is called "Respondent weighting".

Weighting described

Weighting is the process of allocating a weight to each individual record (questionnaire) to rebalance analysis including:

  • To match known population sizes
  • To remove the effects of deliberate over/under sampling of a section of the respondents
  • To compensate for failure to achieve exact quotas
  • To equalize demographics for repeated/continuous surveys

A weight is stored in a float (floating point) entry in every record and for analysis this value is added instead of 1.0 whenever this record enters a table or report.

The desired weighted total value for each subset of the data is called a "target" which can be a figure or a percentage, hence the term "target weighting".

A set responses to an entry with targets is called a "rim", hence the term "rim weighting".

The sum of the targets for a rim will usually be 100%.

Calculating weights

The Companion has a weight procedure which is used to allocate weights to the individual data records.

There is no limit on the number of rims and multi-coded entries can be used.

The outline procedure is usually:

  1. Use [Data] [Weight data] to open the Weight data window
  2. Choose the data file to be weighted
  3. Choose or create the float entry to be used to store the weights
  4. Set and save the targets
  5. Prepare the data and calculate the weights
  6. Check the summary report, especially the ESS
  7. Save the weighting summary report
  8. Save the data with the weights
  9. Save the project (QDF) if a new weight entry was created

Important: Whoever devised the weighting scheme must be informed of the overall ESS/efficiency so that they can decide if the loss of data due to weighting effects is reasonable, or whether they need to simplify the targets to keep more of the data.  It is not unknown for clients to devise comprehensive targets that "throw away" half the data collected through weighting effects.

Where practical the weighting summary report should be saved with the project and sent with any weighted analysis.

Problems with weighting

Sometimes there will be a problem with the targets or the data. This can result in:

  • The program fails to achieve the requested targets
  • The calculations take a very long time

Using with other software

The weighting procedure can be used to weight data which is processed by other software, for example:

  • QPSMR Insight/CATI
  • SPSS
  • triple-s