Acid rain, caused by the reaction of certain air pollutants with rainwater, is a growing problem in the United States. Pure rain falling through clean air registers a pH value of 5.7 (PH is a measure of acidity: 0 is acid; 14 is alkaline). Suppose water samples from 70 rainfalls are analyzed for pH, and x and s are equal to 3.9 and 0.4, respectively. Find a 99% confidence interval for the mean PH in rainfall. (Round your answers to three decimal places.) to Interpret the interval. There is a 1% chance that an individual sample mean will fall within the interval. There is a 99% chance that an individual sample mean will fall within the interval. In repeated sampling, 1% of all intervals constructed in this manner will enclose the population mean. In repeated sampling, 99% of all intervals constructed in this manner will enclose the population mean. 99% of all values will fall within the interval. What assumption must be made for the confidence interval to be valid? There must be at least 100 samples. The sample must be random. The sampling distribution must be symmetrical. The sample mean must be greater than 5. The standard deviation must be less than 10. You may need to use the appropriate appendix table or technology to answer this question. Need Help? Read It Talk to a Tutor Submit Answer Save Progress Practice Another Version -/1 points MendStat14 8.E.037 My Notes O Ask Your Teach as sports utility vehicles. (a) Use a 95% confidence interval to estimate the proportion of sports utility vehicles in California. (Round your answers to three decimal places.) to (b) How can you estimate the proportion of sports utility vehicles in California with a higher degree of accuracy? (HINT: There are two answers. Select all that apply.) increase za/2 by increasing the confidence coefficient decrease Za/2 by decreasing the confidence coefficient increase the sample size n conduct a non-random sample increase za/2 by decreasing the confidence coefficient decrease the sample size n decrease za/2 by increasing the confidence coefficient
