9.45 Unaltered, altered, and partly altered bitumens are found in carbonate-hosted lead-zinc deposits and may aid in the production of sulfide necessary to precipitate ore bodies in carbonate rocks. (See Powell, Science, April 6, 1984, p. 63.) The atomic hydrogen/carbon (H/C) ratios for 15 samples of altered bitumen had a mean of 1.02 and a standard deviation of 0.04. The ratios for 7 samples of partly altered bitumen had a mean of 1.16 and a standard deviation of 0.05. Estimate the difference between true mean H/C ratios for altered and partly altered bitumen, in a 98% confidence interval.
Assume equal population standard deviations.