B
Evidence Grade B
Graded
accuracy verified by the review judge
Safe to Cite
Recent
10%
10% -- sample dropout rate for A/B test samples (CXL) (2025)
Cookie deletion alone causes approximately 10% sample dropout in A/B tests over two weeks.
- Attributed specifically to cookie deletion over a two-week period
Attribution:
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Lighthouse Research Team
Last verified:
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Source verified
Evidence graded
Value
10%
Unit
Percentage
Data Vintage
2025
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
75
Source Trust
60
Citation Chain
20
Independence
30
Methodology
45
Freshness
95
Source
CXL
Primary
Tier B
https://kirro.io/ab-test-sample-size-formula ↗
Source Article
A/B Test Sample Size Formula, Explained With Examples
The A/B test sample size formula is:
n = (Zα/2 + Zβ)² × [p₁(1−p₁) + p₂(1−p₂)] / (p₁−p₂)²
If that looks like gibberish, you’re not alone. Most articles either throw this formula at you with zero explanation, or skip it and say “just use a calculator.”
This guide does both. We’ll break down every piec…
Original Research
CXL
· Original study ↗
Methodology
CXL research on cookie deletion effects
Methodology documented
Segmentation
Industrymarketing
Cite this stat
Plain Text
A/B test samples (CXL): 10% sample dropout rate. Source: CXL (2025). Via Lighthouse Intelligence -- https://lighthousedata.io/data/cookie-deletion-10pct-sample-dropout
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<blockquote cite="https://lighthousedata.io/data/cookie-deletion-10pct-sample-dropout" style="border-left:3px solid #2563eb;padding:12px 16px;margin:16px 0;font-family:system-ui,sans-serif;background:#f0f4ff;"><strong>10%</strong> -- sample dropout rate for A/B test samples (CXL)<br><small>Source: CXL (2025) · <a href="https://lighthousedata.io/data/cookie-deletion-10pct-sample-dropout" target="_blank" rel="noopener">Lighthouse Intelligence</a></small></blockquote>
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