# Hiding Out-of-Stock Items or Offering Notify Me Page: https://alidemirbas.com.tr/en/lab/ab-test-library/tests/hiding-out-of-stock-items-or-offering-notify-me ## Hypothesis If an out-of-stock product stays visible with a "notify me" form, interested visitors may sign up for an alert and come back to buy later; if it is hidden, their attention moves straight to alternatives. Which experience yields the higher purchase rate after an item is out of stock may depend on whether returning buyers outweigh the alternative purchases that hiding prompts. ## When to run this test Out-of-stock pages that still draw search or campaign traffic, high exits from those pages, or support tickets asking when items will be back all make the choice between hiding and notifying worth testing. If the visible arm leads, visitors sign up and return to buy once stock arrives; if the hidden arm leads, clicks on similar products carry the purchases. If exits stem from stale or wrong stock data, fix that first. Before launch, confirm that a visible product never looks purchasable only to fail at checkout, and that alerts go out once the predefined stock condition is met; do not delete or redirect product URLs. ## Primary metric **Purchase rate after an item is out of stock**: Compare purchases, including alternative products, per assigned visitor from a shared eligible entry point over the same fixed follow-up period. ## Other metrics - **Back-in-stock signup rate**: Report signups per assigned visitor in the visible-product arm; the hidden-product arm has no equivalent form. - **Page exit rate**: Compare exits from the experience assigned to each visitor. - **Similar-product click-through rate**: Check whether visitors use the alternative recommendations. ## What to check before and during the test - **Experience**: Compare hiding an out-of-stock product with keeping it visible alongside one fixed back-in-stock form. - **Form**: Keep form fields and eligibility rules unchanged. - **Alternatives**: Use the same rules for alternative products in both arms. - **Assignment**: Assign visitors before product visibility diverges and keep their assignment consistent. ## What to watch when reading the result - The deciding measure is the purchase rate after an item is out of stock over the fixed follow-up period, which includes purchases of alternative products. Back-in-stock signups exist only in the visible arm, so a high signup count does not make that arm the winner by itself. - The result belongs to the whole experience of visibility plus notification, so do not read the gap as the effect of the form alone. Purchases prompted by alerts take time, so compare the arms at the end of the fixed follow-up period, and treat the result as valid for the list or surface you tested. - Out-of-stock pages may draw few visitors, so a short test can leave the difference unclear. Find the visitors you need per arm with the [sample size calculator](https://alidemirbas.com.tr/en/calculators/sample-size-calculator) and divide by daily eligible visitors per arm to get the run length. Then add the fixed follow-up period on top. ## Frequently Asked Questions ### Does this test isolate the stock-notification form’s effect? No. Visibility and notification access change together. Interpret the complete experience rather than attributing the result to the form alone. ### Why are notification signups not the primary outcome? Control has no equivalent form. Use purchases per assigned eligible visitor as the primary outcome, including alternative purchases over the same window. ### What matters when keeping an unavailable product visible? Show availability accurately. Record the requested notification, provide the applicable privacy notice and send only the requested content. Handle required commercial-message permissions separately rather than conflating them with privacy disclosure. ### Should product URLs be deleted in the hidden arm? No. Do not delete or redirect them for this experiment. Assign before the visibility difference and preserve assignment while testing the visitor experience.