To measure the success of using a gift card promotion to get Prime members to download the Prime mobile app, we can design a test that includes the following steps: 1. Define the success metrics: We need to identify the key performance indicators (KPIs) that will help us measure the success of the promotion. These KPIs could include the number of Prime members who downloaded the app, the number of gift cards redeemed, the total revenue generated by the promotion, and the increase in overall app engagement. 2. Define the target audience: We need to identify the specific segment of Prime members who will be targeted by the promotion. This could be based on factors such as demographics, location, or previous app usage. 3. Design the promotion: We need to determine the specifics of the gift card promotion, such as the value of the gift card, the duration of the promotion, and the messaging used to promote the offer. 4. Launch the promotion: We need to roll out the promotion to the targeted Prime members, using a variety of channels such as email, push notifications, and in-app messaging. 5. Monitor the KPIs: We need to track and analyze the KPIs identified in step one throughout the promotion period to determine the effectiveness of the promotion. 6. Analyze the results: After the promotion is complete, we need to analyze the data collected during the promotion period to determine the success of the promotion. This could involve comparing the KPIs to historical data or to a control group that did not receive the promotion. 7. Iterate and improve: Based on the results of the analysis, we can make adjustments to the promotion strategy and iterate on the promotion to improve its effectiveness. By following these steps, we can design a test that will help us measure the success of using a gift card promotion to get Prime members to download the Prime mobile app.