You're a civil engineer testing the compressive strength of concrete to be used in bridge construction. You test 16 concrete specimens, the resulting in the following compressive strengths (in psi). Determine if the standard deviation of compressive strength is less than 50 psi with 95% confidence with the critical value approach. 2223 2329 2269 2244 2258 2325 2204 2296 2316 2272 2302 2342 2307 2205 2208 2311