A computer battery is found to have a mean time between charges of 13 hours. A modification is made which is supposed to increase battery life. Test on a random sample of 35 modified computers resulted in mean battery life of 13.6 hours with a standard deviation 0.5 hours. At the 95% confidence level, test the claim that the mean time between charges is longer after the modification.

Dexter read 11 science fiction books and 5 history books. lena read 9 science fiction books and 4 history books. compare the students’ ratios of science fiction books to history books. 1. determine the ratios’ form:    science fiction books to history books 2. write the ratios as fractions:    dexter: 115; lena: 94 3. rewrite with a common denominator. 4. compare. 5. answer the question. determine which shows the correct comparison of the ratios for this problem.