When the KPI is not revenue (total paid media contribution prior)

When the KPI is not revenue, we recommend providing the value or an estimate of revenue_per_kpi. Providing this means that incremental outcome is in terms of monetary units (such as dollars), not KPI. Meridian defines ROI as incremental outcome divided by spend. So when incremental outcome is in terms of monetary units, ROI is a unitless quantity. This makes the default ROI priors a reasonable choice for most use-cases.

However, sometimes there isn't a clear monetary unit associated with the KPI and no reasonable revenue_per_kpi argument can be used. For example, the number of free app installations where the lifetime value of an app installation isn't known within a reasonable margin of error. In this scenario, we recommend using custom priors. For more information, see Custom priors when outcome is not revenue.

If it is not possible to set a custom prior based on your use case, we recommend using the default total paid media contribution prior.

Default total paid media contribution prior

When all of the following are true:

• The KPI is not revenue.
• revenue_per_kpi is unavailable.
• media_prior_type is 'roi' and rf_prior_type is 'roi'.

The default ROI prior is not used and, instead, a common ROI prior is placed on all channels such that the proportion of the KPI that is incremental due to all paid media channels has a prior mean of 40% and standard deviation of 20% (referred to as a "total paid media contribution prior"). In this case, ROI is interpreted as incremental KPI units per spend unit. To set the prior mean and standard deviation to something other than 40% and 20%, see Custom total paid media contribution prior.

Note that Meridian will default to this behavior when the KPI is not revenue and revenue_per_kpi is not set, so there is no need to specify the ROI prior separately in the prior container. If a ROI prior is explicitly set, then Meridian will use this over the default.

This "total paid media contribution prior" is not the same as channel-level contribution priors. See Set custom priors when outcome is not revenue for a description of channel-level contribution priors.