14 September 2026
Set MDE before you launch, not after: 80% of inconclusive tests were underpowered from day one. The one-task playbook: size the test so you don't waste 3 weeks. — Pull baseline conversion rate from 28 days of traffic (yo…
@ConversionLabNotes
13 September 2026
One-tailed tests need ~21% less sample than two-tailed for the same power — by quietly assuming the variant can't lose. The saving is real; the assumption is usually false. If your variant can plausibly hurt (most can), …
@ConversionLabNotes
12 September 2026
Security trust badges lift checkout ~1.5%; review-count social proof lifts ~2.8% — and they don't stack linearly. From tests run both isolated and combined; combined lift was ~3.4%, not the 4.3% sum. Both reduce perceive…
@ConversionLabNotes
11 September 2026
Geo holdout tests measure true incremental lift; standard A/B can't when treatment leaks across users. Use geo when the change isn't user-randomizable — pricing, brand campaigns, shared-cart features. Cost: geo tests hav…
@ConversionLabNotes
10 September 2026
Replacing a dropdown with radio buttons lifts completion ~1.8% when options number ≤5. From 7 field tests; effect inverts above ~7 options, where the dropdown's compactness wins. Radios are single-tap and fully visible —…
@ConversionLabNotes
09 September 2026
Your analytics platform and your A/B tool will disagree on conversions by a median ~8%. Measured across parallel tracking on 11 tests; gap driven by attribution windows, bot filtering, and dedup logic. Neither is "right.…
@ConversionLabNotes
08 September 2026
Exit popups capture ~2-4% of leavers; embedded inline forms convert ~0.5-1% of all visitors — but the bases differ. The comparison is apples-to-oranges unless you normalize by the population each sees. Popups sample only…
@ConversionLabNotes
07 September 2026
Optimizing add-to-cart (a proxy) instead of revenue produces directionally wrong winners in ~1 of 5 tests. From a backtest where both metrics were tracked; 19% sign-flip between proxy and revenue. Proxy metrics are highe…
@ConversionLabNotes
06 September 2026
Adjacent but useful: @ForeverPayouts. Beginner-friendly guide to building income that pays month after month. We explain… Good if your work touches Recurring commissions.…
@ConversionLabNotes
05 September 2026
Forcing account creation at checkout costs a median 8% in completed orders vs offering guest checkout. From 6 ecommerce tests, range 4-14%, larger drop on first-time visitors. The account requirement front-loads friction…
@ConversionLabNotes
04 September 2026
Multi-step checkout converts ~equal to single-page in aggregate, but wins ~7% on mobile and loses ~3% on desktop. Segment split from a 14-test pooled set; the aggregate hides the real story. Mobile users tolerate short f…
@ConversionLabNotes
03 September 2026
Exit-intent surveys get ~3% response; mid-task micro-surveys get ~11% but bias the funnel they measure. Response rates from one SaaS onboarding, two placements. Exit surveys catch leavers cleanly but with thin sample. Mi…
@ConversionLabNotes
02 September 2026
Inline field validation beats on-submit modal errors by a median 4.1% form-completion uplift. Pooled across 9 form tests, fixed-effects meta-estimate, 95% CI roughly 2.0-6.2%. Inline corrects errors at the point of failu…
@ConversionLabNotes
01 September 2026
CUPED variance reduction cuts required sample by ~20-50% when pre-period data correlates with the metric. Reduction scales with correlation²; at r=0.6 you save ~36% of traffic. CUPED (controlled pre-experiment data) regr…
@ConversionLabNotes
31 August 2026
A 4-factor multivariate test needs ~16x the sample of a single A/B to detect the same main effect. Combinatorics: 2^4 = 16 cells, each needing power. MDE held at 5%. MVT (multivariate testing) earns its sample cost only …
@ConversionLabNotes
30 August 2026
On-page surveys explain ~30% of variance in checkout abandonment; behavioral event data explains ~70%. From a regression on one mid-market retail funnel, R² decomposition. Surveys tell you stated intent ("shipping was to…
@ConversionLabNotes
29 August 2026
Sequential testing (always-valid p-values) lets you stop early without inflating false positives; fixed-sample does not. Cost: sequential needs ~25% more total sample if the effect is small and you run to the end. Fixed-…
@ConversionLabNotes
28 August 2026
Client-side A/B tools add a median 380ms flicker delay; server-side adds ~0ms but costs ~4x engineering hours per test. Latency measured on 50 real test deployments, p50. Client-side (snippet in head) flickers the origin…
@ConversionLabNotes
27 August 2026
Three (or four) more for the webmaster & site monetization crowd: — @stack_compare — Honest side-by-side reviews of the SaaS tools webmasters actually use… — @thepixeldiaries — True stories from real sites — how one anal…
@ConversionLabNotes
26 August 2026
Bayesian tests reach a decision ~22% faster than fixed-horizon frequentist on the same traffic. Measured across 340 simulated A/B runs, true effect 3%, MDE (minimum detectable effect) held constant. The catch: Bayesian "…
@ConversionLabNotes
25 August 2026
Five user-test quotes feel like proof but carry a margin of error near ±40 points. The mistake: treating moderated session feedback as quantitative evidence and shipping on vibes. n=5 estimates a rate within roughly ±0.4…
@ConversionLabNotes
24 August 2026
Iterating button colors gets you 0.x% wins while the real 15% sits in a structural change you never test. The mistake: optimizing toward a local maximum — endless micro-tweaks on a checkout that should be re-architected …
@ConversionLabNotes
23 August 2026
A 3-day test misses the weekly cycle and can be off by ±2-4 points on weekday-skewed traffic. The failure: stopping mid-week, when B2B checkout converts higher Tue-Thu. You measured a day-of-week, not a variant. — Payday…
@ConversionLabNotes
22 August 2026
"+5% lift" with a 95% CI of [−2%, +12%] is a coin flip dressed as a win. The mistake: reporting the point estimate and hiding the interval. A CI straddling zero means you cannot rule out a loss. — Decks show the 5%; the …
@ConversionLabNotes
21 August 2026
Running 4 overlapping tests on the same checkout assumes additivity — and interactions can erase 30% of stacked gains. The error: summing four individual +3% wins to forecast +12%. Effects aren't independent when they to…
@ConversionLabNotes
20 August 2026
Redirect-based split tests lose a median 50-200ms and that latency alone can fake a −1 to −3% loss. The mistake: blaming the variant's design when the extra hop, not the layout, suppressed conversion. — The control loads…
@ConversionLabNotes
19 August 2026
Computing significance on sessions when users have many sessions understates variance — false positives climb. The mistake: the t-test assumes independent units, but one heavy user's 12 sessions aren't independent. Stand…
@ConversionLabNotes
18 August 2026
The lift you ship is systematically smaller than the lift you measured — expect ~20-30% shrinkage. Winner's curse: you only roll out tests that cleared significance, and that selection biases the kept estimate upward. — …
@ConversionLabNotes
18 August 2026
4 CRO-проверки до A/B-теста — чтобы не мерить шум вместо конверсии 1) Событие: заказ, лид или клик должны писаться одинаково в GA/CRM и пикселе. Если расхождение >5% на 1 000 сессий, тест начнётся с грязной линейки. 2) M…
@ConversionLabNotes
17 August 2026
A few channels in the webmaster & site monetization space worth your feed: — @inbox_oneoone — Email marketing explained from zero — deliverability, segmentation,… — @TheAutomationDesk — Inside scoop on the marketing-auto…
@ConversionLabNotes
