A 3% margin of error means that if the same procedure is used a large number of times, 95% of the time the true population average will be within the 95% confidence interval of the sample estimate plus or minus 3%.
The latter is a fairly common problem which is associated with people who have the condition known as hypothyroidism. Despite what many people think, tinnitus is actually just a symptom of a larger underlying problem. Hypothyroidism is just one of the many health problems which can cause tinnitus to become a problem. In most cases when the thyroid dysfunction is treated, the tinnitus will resolve itself. There have been some cases of people with this condition who suffer from long-term tinnitus, though that is usually not the case.
Hypothyroidism is treated with medicine that gives your body the thyroid hormone it needs to work normally. The most common medicines are man-made forms of the hormone that your thyroid makes. You will likely need to take thyroid hormone pills for the rest of your life.