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2% difference in Uniques and ROLLWIN(UNIQUE, A, 30)

  • 13 June 2022
  • 2 replies
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Hi all,

 

I have a chart that shows the rolling window of unique users in the last 30 days. If I then switch from the formula to the Uniques option in a bar chart the total number of unique visitors is suddenly 2 % higher than that of the rolling window of unique users in the last 30 days. 

Is there anybody that has seen this before and can explain to me why the Uniques bar chart in the last 30 days is showing a higher number than the rolling window of unique users in the last 30 days?

 

Kind regards,

Quint

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Best answer by Saish Redkar 13 June 2022, 17:51

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Hey @quint 

I tried replicating this one and looks like “Last 30 days” from a given point returns more than rolling 30 day window.

Here’s a demo chart outlining the scenario - https://analytics.amplitude.com/demo/chart/new/9fx6vjd

I’m not 100% sure about the reason here, but I think it’s due to how the calculation is done by the 2 different approaches. I suspect that last 30 days is taking the entire day ( 24 hrs ) of the beginning day to be included in the calculation. Whereas rolling 30 days might be cutting off the calculation to the last hour relative to the point in time on the day of the query. So based on the query time, rolling formula might not account for the full 24 hours of May 14th in case of the demo chart.

 

Hope this helps.

 

 

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Hi Saish,

 

That makes sense. Thanks for the response.

 

Kind regards,

Quint

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