Researchers compared the effects of two different medications on reducing blood pressure. From random samples of patients, they calculated a 99% confidence interval for the difference in mean reduction (Medication X - Medication Y) as (3.5, 12.8) mmHg. A colleague reviews this and states: “We can be 99% certain that the true difference in mean blood pressure reduction between these medications falls between 3.5 and 12.8 mmHg.” What key element is missing from this interpretation?