Allow using different scales for different channels?

[ykhirano]

Hi there.

I'm trying to run Meridian with media inputs that have different scales.
For example:

media=[
        'Channel0_grp',
        'Channel1_impression',
        'Channel2_impression',
        'Channel3_impression',
        'Channel4_impression',
        'Channel5_click',
    ]

Since the data is standardized during estimation, the model results themselves look fine.
However, the "ROI vs. effectiveness" visualization seems incorrect because of the different scales.

Meridian may require to use the same unites across all media,
but is there any correct way to display or interpret this when the scales differ?

[cpulavarthi]

Hello @ykhirano,

Thank you for contacting us!

I can see that you are using a mixture of exposure metrics (GRP, impressions, and clicks) for your media channels. Comparing effectiveness estimates while using different exposure metrics is not possible. This is because “effectiveness” is defined as the incremental revenue gained per media unit.

One GRP might represent millions of impressions, and one click is a much more valuable outcome than one impression. Comparing the revenue from "1 impression" to the revenue from "1 click" will naturally show clicks as having higher effectiveness. Hence these units are fundamentally incomparable.

Even if all these exposure metrics were to be pre-scaled to be in similar ranges, the interpretation of results will be far more complicated. You wouldn’t simply be comparing the effectiveness of different media channels, the media impact mechanism would also be fundamentally different for different metrics thus making the effectiveness comparison more complicated, i.e., if one channel proves to be more effective than the other, it is difficult to determine if this is because the channel is inherently better or because of the exposure metric used. Additionally, pre-scaling exposure metrics isn’t recommended in the first place as it will result in the data being scaled twice.

There is no workaround that can help you directly compare the effectiveness of different channels on one plot at the same scale. When you are using different exposure metrics you will need to use your business judgement and understanding of the metrics themselves to compare the effectiveness estimates, if that is desired. Meridian does not include a methodology to do that for you.

Feel free to reach out if you have any questions or suggestions regarding Meridian.

Google Meridian Support Team