Once the experiment is finished, next step is to analyze the results. A/B Testing tool will present the data from the experiment and will tell you the difference between how the various variations on a web page performs, and also if there is a important difference between variations, using the assistance of mathematical techniques and statistics.
If the images on a website page has reduced the bounce rate, you can decide whether it has a good conversion or not, when you upload more pictures on a web page. If you see no change in the bounce rate because of this, go back to the previous step and create a new hypothesis/variation to perform a another test.
Tools like VWO and Optimizely are utilized to run tests, but Google Analytics is most suited to run post-test analysis. This analysis is utilized to decide the way going forward. A/B Testing tools tell about the outcome of a test result, but there is a need to perform post analysis as well. To do post analysis you need to integrate each test with Google Analytics.
Both VWO and Optimizely gives built-in Google Analytics integration capability. The data for each test from both these tools should be sent to Google Analytics. By doing this, it upgrades your analysis capabilities and ensures testing data. There is a possibility that your testing tool might be recording the data incorrectly, and if you have no other source for your test data, you can never be sure whether to trust it or not.