Another method for dating rocks was used before the advent of the potassium-argon method described in Case Study 7.5.1. Because of a mineral’s lead content, it was capable of yielding estimates for this same time period with a standard deviation of 30.4 million years. The potassium-argon method in Case Study 7.5.1 had a smaller sample standard deviation of √733.4 = 27.1 million years. Is this “proof” that the potassium-argon method is more precise? Using the data in Table 7.5.1, test at the 0.05 level whether the potassium-argon method has a smaller standard deviation than the older procedure using lead.