1 (If you don't know what these, are set them each to 0.5. 2  z is the value that specifies the level of confidence you want in your confidence interval when you analyze your data. 3  Typical levels of confidence for surveys are 95%, in which case z is set to 1.96. 4  E sets the accuracy of your sample proportions.
Tests and diagnosis discussion for Gallstones: Many gallstones, especially silent stones, are discovered by accident during tests for other problems. But when gallstones are suspected to be the cause of symptoms, the doctor is likely to do an ultrasound exam. Ultrasound uses sound waves to create images of organs.
The most common technique is an ultrasound exam. This quick, painless procedure uses high-frequency sound waves to create pictures of the gallbladder, bile duct, and their contents. CT scans are also sometimes done to look at the anatomy of your internal organs. A more complicated test may be used if the doctor suspects that a gallstone is lodged in a bile duct.