An aspirin manufacturer has designed the child- proof cap on its bottles so that it must be pressed down before it can be turned and removed. A consumer maga- zine has randomly purchased 15 bottles of the company's aspirin for analysis in a feature article on pain relievers and their packaging. Among the analyses is a test of how much force is required to depress the cap on each bottle. The standard deviation for the bottles made by this man- ufacturer is found to be 7.2 grams. From the magazine's findings, and assuming a normal distribution, determine the 95% confidence interval for the population standard deviation of the force required to depress the firm's aspi- rin bottle caps.