As you already know, I'm a big proponent of the scientific experimentation method. You can never truly know or guess which main image will attract more customers to your product page or which title will make Amazon's algorithm rank you higher in search results.
After years of using external tools to conduct these tests, Amazon is now launching a free tool for brand owners that allows you to perform smart A/B tests in three areas:
Designed A+ content
Here's how it works:
Let's say you have a product that's suitable for both young and older women, and you want to know which main image works better. You upload two different images to the testing system, one with an older woman and the other with a younger woman, and Amazon evenly and randomly distributes exposure to your product at a 50/50 ratio.
So, when you search for your product in the search results, you'll see one image, and when you refresh the page, you'll see the other image (unlike external tools that changed the image once a day).
After a few days, you can measure the results, gather all the data from Amazon about exposure, clicks, conversions, and so on, and decide which image performed better to continue with.
You can find this feature in the navigation menu:
Brands - Manage Experiments
Good luck with your A/B testing!