Ad copy tests are experiments; the results are intended to provide you with additional data to make decisions about your creatives. The results aren't intended to guarantee an ad's performance. If a test collects enough data to indicate that the test results aren't random, meaning that the test is significant, then you are likely to see the same performance if you repeat the test.
Examples:
Result: Is significant
If an ad copy test result is significant, and one ad performed better than the other ads, you can stop the poor performing ads. The best ad will continue to perform within the range specified by the confidence interval.
Ad copy test settings
Goal = CTR
Statistical significance threshold = 95%
Ad copy test results for an ad
Confidence interval = 3.92% to 4.27%
The result indicates that you can be 95% certain that the true value of the CTR for the better performing ad is between 3.92% and 4.27%.
Result: Not significant
If an ad copy test result is not significant, and all of the ads in the test perform about the same, you can stop the test and continue to run the ads.
Ad copy test settings
Goal = Action rate
Statistical significance threshold = 90%
Ad copy test results
Confidence interval for all of the ads ranges from 81.65% to 90.88%
The result indicates that there isn't a significant difference in ad performance. You can stop the test without pausing any of the ads. If you want to test more, consider adding more ads to the ad group and then start a new test.
Result: Is significant
An ad copy test can be significant with all of the ads rated undecided.
Ad copy test settings
Goal = CTR
Statistical significance threshold = 95%
Ad copy test results
The confidence intervals show that Ad1's CTR is between 1.55% and 1.80%. Ad2's CTR is somewhere between 1.33% and 1.56%. The results indicate that it's possible, but unlikely, that Ad2 could outperform Ad1.
You have at least two options with such results. Because Ad1 performed slightly better, you can stop the test and pause Ad2. This will probably increase the CTR. Or, you can stop the test and let both ads continue to run.
Result: Is significant
An ad copy test can be significant and identify poor performing ads with undetermined ad performance.
Ad copy test settings
Goal = Revenue/visit
Statistical significance threshold = 90%
Ad copy test results
The result indicates you can be 90% certain that you can stop the test and pause the poor performing ads. The other ads will continue to perform within the ranges specified.