The group of households I want to survey with the PPI are not nationally representative. How does this affect the results?

The PPI scorecard is based on data from a nationally representative group of households. When you apply the survey to a group of households that are not nationally representative – such as a group of farmers or a group of women – there will be 'out of group bias'. Organizations that use the PPI will usually encounter out of group bias because they have designed their services to meet the needs of households and individuals with specific characteristics, or because they do not operate across the entire country.

Most organizations cannot avoid this bias, and since the bias will be different in every case, we cannot predict the bias ahead of time. Those responsible for analyzing PPI results and making strategic decisions based on those analyses should consider how their unique context may affect PPI results.