A company wants to check the consistency of electronic copies of signatures for consumer credit purchases. A sample of 49 electronic signatures are available from the same customer. One measure of consistency in signing is the total length that the script is outside the signature box. The sample of 49 signatures yielded a mean length of .21 with a standard deviation of . 19 centimeter.
Obtain a 99% confidence interval for this customer's population mean length outside the box.