Oxygen demand is a term biologists use to describe the oxygenneeded by fish and other aquatic organisms for survival. TheEnvironmental Protection Agency conducted a study of a wetlandarea. In this wetland environment, the mean oxygen demand was μ =9.8 mg/L with 95% of the data ranging from 6.0 mg/L to 13.6 mg/L.Let x be a random variable that represents oxygen demand in thiswetland environment. Assume x has a probability distribution thatis approximately normal. (a) Use the 95% data range to estimate thestandard deviation for oxygen demand. (b) An oxygen demand below 8indicates that some organisms in the wetland environment may bedying. What is the probability that the oxygen demand will fallbelow 8 mg/L? (Round your answer to four decimal places.) (c) Ahigh oxygen demand can also indicate trouble. An oxygen demandabove 12 may indicate an overabundance of organisms that endangersome types of plant life. What is the probability that the oxygendemand will exceed 12 mg/L? (Round your answer to four decimalplaces.)
