Reading Experiment Results
Reading experiment results
To read the results of your experiment, go to the Results tab, where you will see your experiment exposures, and then Metric Lifts. The Metric Lifts section has two main tabs- Scorecard and All Metrics.
Scorecard shows the metric lifts for all Primary and Secondary metrics you set up at experiment creation as part of the Scorecard. All Metrics shows the experiment impact for all metrics in your Metric Catalog, regardless of whether they were included in the Scorecard or not.
- Experiment results are computed for the first 90 days: By default, Statsig will compute Pulse Results for your experiment for only the first 90 days of your experiment. You will be notified via e-mail as you approach the 90 days cap, at which point will be able to extend this compute window for another 30 days at a time. Your user assignment will continue to run as expected even if the compute window is not extended, until you make a decision on the experiment.
The Scorecard panel shows how your Primary and Secondary experiment metrics for each variant compare against the control. These Primary and Secondary metrics are in the context of the experiment hypothesis, which is also prominently highlighted at the top of the Scorecard tab.
All Scorecard metrics by default have CUPED (Controlled-Experiment Using Pre Experiment Data) applied to them. CUPED is a statistical technique first popularized for online testing by Microsoft in 2013 that leverages pre-experimental data to reduce variance and pre-exposure bias in experiment results. Tactically, CUPED can significantly shrink confidence intervals and p-values, ultimately reducing the sample size and duration required to run an experiment. To read more about CUPED, see this blog post as well as our docs on variance reduction.
In the example below, the Circle variant has a statistically significant lift in the add_to_cart and product_view metrics. However, the Square variant is not seeing any statistically significant lifts on any metric. This is represented by the gray Overall Lift symbols and large p-values.
When you mouse over a metric lift, additional, more detailed information on the metric lifts is displayed. This includes:
- Unit counts, means, and totals for each experiment group
- Ability to see a time series of how the lift has trended by day, days since exposure, and cumulatively
- Raw data for the lifts
- Topline metric impact and projected topline impact at launch (if this experiment were to roll out to 100%) Read more about how to interpret the detailed Pulse results presented in the hovercard here.
The All Metrics tab shows the metric lifts across all the metrics in your Metrics Catalog. To prevent a metric from showing up in Pulse, you can hide it via Metrics tab. Simply search for the metric in the Metrics Catalog, tap on it to go to the Metric Detail View, tap the ... menu in the upper right-hand corner, and select Hide.
Significance Level Settings
These settings can be adjusted at any time to view Pulse results with different significance levels.
- Apply Bonferroni Correction: Select this option to apply the correction in experiments with more than one test group. This reduces the probability of Type I errors (false positives) by adjusting the significance level alpha, which will be divided by the number of test variants in the experiment.
- Confidence Interval: Changes the confidence interval displayed with the metric deltas. Choose lower confidence intervals (e.g.: 80%) when there's higher tolerance for false positives and fast iteration with directional results is preferred over longer/larger experiments with increased certainty.
- CUPED: Toggle CUPED on/ off via the inline settings above the metric lifts. NOTE- this setting can only be toggled for Scorecard metrics, as CUPED is not applied to non-Scorecard metrics.
- Sequential Testing: Applies a correction to the calculate p-values and confidence intervals to reduce false positive rates when evaluating results before the target completion date of the experiment. This helps mitigate the increased false positive rate associated with the "peeking problem". Toggle Sequential Testing on/ off via the inline settings above the metric lifts. NOTE- this setting is available only for experiments with a set target duration.