B
Evidence Grade B
Graded
accuracy verified by the review judge
Safe to Cite
Current
30%
30% -- sample size reduction from variance reduction for CUPED (variance reduction) (2026)
Using CUPED for variance reduction yields 30 to 40% smaller sample sizes while maintaining the same precision.
- Requires existing visitor data to reduce variance
Attribution:
View source
Lighthouse Research Team
Last verified:
·
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Source verified
Evidence graded
Value
30%
Unit
Percentage
Data Vintage
2026
Entity
Evidence Quality
B
Strong, reliable evidence
Sourced from a well-regarded research firm or industry leader with transparent methodology and a reasonably large sample.
Single source - not yet corroborated
Score breakdown
Extraction
50
Source Trust
60
Citation Chain
20
Independence
30
Methodology
45
Freshness
95
Source
kirro.io
Primary
Tier C
https://kirro.io/testing-methodology ↗
Source Article
A/B testing methods: pick the right one | Kirro
Only 1 in 7 A/B tests reach statistical significance. That’s an 86% failure rate. And yet 58% of companies have no framework for deciding what or how to test.
Those two stats are connected. Bad methodology is why most tests fail. Not bad ideas.
This section covers the science behind reliable testing…
Original Research
kirro.io
· Original study ↗
Methodology
Range 30-40%; midpoint extracted
Methodology documented
Segmentation
Industrymarketing
Cite this stat
Plain Text
CUPED (variance reduction): 30% sample size reduction from variance reduction. Source: kirro.io (2026). Via Lighthouse Intelligence -- https://lighthousedata.io/data/cuped-sample-size-reduction
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<blockquote cite="https://lighthousedata.io/data/cuped-sample-size-reduction" style="border-left:3px solid #2563eb;padding:12px 16px;margin:16px 0;font-family:system-ui,sans-serif;background:#f0f4ff;"><strong>30%</strong> -- sample size reduction from variance reduction for CUPED (variance reduction)<br><small>Source: kirro.io (2026) · <a href="https://lighthousedata.io/data/cuped-sample-size-reduction" target="_blank" rel="noopener">Lighthouse Intelligence</a></small></blockquote>
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