# Sticky add-to-cart bar with size picker: +7.6% ATC, inconclusive

- Outcome: Flat / inconclusive
- Page type: Product page (Ecommerce)
- Elements: Sticky add-to-cart bars, Variant, size & option selectors
- Test run by: [Clean Commit](https://liftarchive.com/practitioners/clean-commit/)
- Commentary by: LiftArchive (our analysis, not theirs)
- Original source: https://cleancommit.io/ab-tests/sticky-bottom-add-to-cart-bar/
- Page: https://liftarchive.com/test/cleancommit-sticky-bottom-add-to-cart-bar/

Adding a sticky add-to-cart bar with size and color dropdowns to AFTCO's mobile product pages lifted add-to-cart rate 7.6%, but we treat the result as inconclusive. Clean Commit ran this test for AFTCO and published it in its A/B test library. Clean Commit labelled it inconclusive too, and revenue fell because average order value dropped.

## Result

**+7.6% ATC, inconclusive**

- Add-to-cart rate: +7.6%, the headline number, but not shown to be significant.
- Conversion rate: +2.1%, a much smaller lift than add-to-cart.
- Average order value: -5.2%, and Clean Commit reported that revenue fell as a result.
- Bounce rate: -8.2% and click-through rate +5.1%, so shoppers engaged more with the page.

## Control

The mobile product page had no sticky add-to-cart bar. Shoppers used the standard size, color and add-to-cart controls on the page.

## Variant

A sticky bar stayed on screen with size and color dropdowns, an add-to-cart button and a 'Find my size' link.

## Why it likely came out this way (our reading)

- Keeping size and color choices in reach saves shoppers from scrolling back up, which likely explains the add-to-cart lift.
- A quick-buy bar may push shoppers to add one item and go, rather than browse more, which fits the lower order value.
- Most of the extra add-to-carts didn't turn into orders, so the lift may be noise or low-intent adds.

## Caveats

Clean Commit labelled this test inconclusive and shared no sample size, duration or confidence level. Revenue fell because of lower order value.

## How to run this test

- Hypothesis: If we add a sticky mobile bar with size and color dropdowns, then more shoppers will add to cart because they won't need to scroll back to the options.
- Primary metric: Mobile conversion rate
- Guardrail: Average order value
- Guardrail: Revenue per visitor
- Guardrail: Add-to-cart rate
- Who should test it: Apparel and footwear stores with long mobile product pages and several sizes or colors. If your order value depends on bundles or add-ons shown lower on the page, watch revenue closely.

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Credit: Clean Commit ran this test and owns the result. Summary and commentary by LiftArchive (https://liftarchive.com/test/cleancommit-sticky-bottom-add-to-cart-bar/).
Usage: Free to use, quote and build on, with credit and a link: name the practitioner or organization that ran the test and link to its LiftArchive page. The results belong to the practitioners who ran and shared them; the summaries and commentary are LiftArchive's.