Product Detail Page
Size Selection in a Bottom Sheet or Inline A/B Test
A bottom sheet groups sizes in a focused panel while keeping the product page behind it. Inline options remove the opening step but may be farther down the screen. Neither format guarantees one-handed use; compare completed add-to-cart actions with the same size choices.
A/B test scenario. This page is a test plan, not the result of a real experiment.
- Product page
- Add-to-cart rate
Option A vs Option B
Two alternatives; neither is the incumbent.
- Changed
- Options
- Page
- Product page
- Difference
- changed
Hypothesis
On a long mobile product page, if inline sizes sit off screen, the focused bottom sheet panel could make choosing easier. When the sizes are already in view, the extra opening step may become friction instead. Which format pulls ahead on add-to-cart rate with a size selected may depend on where the selector sits on the page.
Test plan
When to run this test
Session recordings of mobile shoppers hunting for the size selector or opening and closing the size options over and over, or taps on add to cart before any size is chosen, show that picking a size has become a struggle. If one container suits the page layout better, it lets shoppers finish size selection with less back-and-forth, and add-to-cart follows. If the friction comes from stock information or the size chart, look there first. Check before you start that the sheet has a visible close button, stays within the predefined half-screen limit with every control usable, and keeps the scroll position.
How to measure success
Add-to-cart rate
Compare successful add-to-cart events with a size selected per eligible assigned visitor.
Also track
- Size selection completionUse the same eligible starting population in both arms.
- Purchase conversion rate (CR)Check whether the result carries through to purchases.
- Size-related return rateTrack size-related returns over the same follow-up period.
- Return-to-page usabilityCheck that closing the sheet preserves the usable page and prior scroll position.
How to set it up
- ContainerCompare the same selector in a bottom sheet and inline on the page.
- DiscoverabilityKeep stock information and size availability unchanged.
- AccessReview touch interactions on the targeted mobile layouts.
- PlatformReview each supported platform separately.
- Unavailable sizesKeep the same disabled-size treatment in both arms.
What to watch when reading the result
- 1The comparison rests on add-to-cart rate with a size selected. Measure size selection completion over the same eligible starting population in both arms; leaving out visitors who never open the sheet flatters that arm. More adds that come with lower purchase conversion or more size-related returns are a warning, not a win.
- 2Keep the size chart in the same place in both arms, so the result speaks only to the container and does not automatically carry over beyond the mobile layouts you tested. Read each supported platform on its own, and compare size-related returns once orders in both arms are past the follow-up period.
- 3When the arms come out close, use return-to-page usability and touch interactions to see which arm is causing trouble. Work out how many visitors you need to detect the smallest difference worth acting on with the sample size calculator, and divide that sample per variant by daily mobile traffic per arm to plan the run.
Frequently Asked Questions
How can size-selection completion be compared fairly?
Use the same eligible starting population, including users who never open the sheet. Use successful add-to-cart with a valid size as the primary outcome.
What should be checked in the bottom sheet?
Verify dismissal, focus, preserved selection and return to the expected page position. Keep contents usable on supported screens and unavailable sizes unselectable.
What matters if add-to-cart improves?
Apply the purchase and size-return guardrails over equal follow-up windows. Inspect supported platforms separately rather than assuming more cart additions become completed sales.
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