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Unit Count (One-Time Event) Metrics

Summary​

Unit count metrics with the one-time event rollup type measure if a unit performed an action any time after being exposed to the experiment.

Use Cases​

This is an extremely common metric type, used to measure participation rates among users in the experiment.

Calculation​

At the unit level, unit count metrics create a 1/0 flag for if they participated.

At the group level, the mean is calculated as the SUM of the unit-level flags, divided by the count of UNIQUE UNITS exposed to the experiment.

This would look like the SQL below:

-- Unit Level
SELECT distinct
  unit_id,
  group_id,
  1 as value
FROM source_data;

-- Experiment
SELECT
  group_id,
  COUNT(distinct unit_id) total_units
FROM exposure_data
GROUP BY group_id;

-- Group Level
SELECT
  group_id,
  SUM(value)/SUM(total_units) as mean
FROM unit_data
JOIN group_data
USING (group_id)
GROUP BY group_id;

Methodology Notes​

Unit count metrics are simple, and will use the sql SUM aggregation. However, there are many advanced options you can apply.

Options​

  • Metric Breakdowns
    • You can configure Metadata Columns to group results by, getting easy access to dimensional views in pulse results
  • Multi Source
    • Sums can be built with inputs from multiple metric sources; think of this as a UNION in SQL. This can be useful if you have the same measure in sharded or disparate tables
  • Rollup Mode
    • Rollup Mode controls the specific way that Unit Count metrics are aggregated