Our environment is very sensitive to the amount of ozone in the upper atmosphere. the level of ozone normally found is 6.0 parts/million (ppm). a researcher believes that the current ozone level is not at a normal level. the mean of 26 samples is 6.2 ppm with a variance of 0.36. assume the population is normally distributed. a level of significance of 0.05 will be used. make the decision to reject or fail to reject the null hypothesis.

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.

In need of in the diagram, ∠abc is a right angle. ∠dbc = 30°27'40". find the measure of ∠abd.

Graph the equationy=x^2 -[tex]y = x^{2} - 2[/tex]