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The Safe Drinking Water Act, which was passed in 1974, allows the Environmental Protection Agency (EPA) to regulate the levels of contaminants in drinking water. The EPA requires that water utilities give their customers water quality reports annually. These reports include the results of daily water quality monitoring, which is performed to determine whether drinking water is safe for consumption.
A water department tests for contaminants at water treatment plants and at customers laps. These contaminants include microorganisms, organic chemicals, and inorganic chemicals such as cyanide. Cyanide’s presence in drinking water is the result of discharges from Steel, plastics, and fertilizer factories. For drinking water, the maximum contaminant level of cyanide is 0.2 part per million.
As part of your job for your city’s water department, you are preparing a report that includes an analysis of the results shown in the figure at the right. The figure shows the point estimates for the population
3. What Do You Think?
The confidence interval for Year 2 is much larger than the other years. What do you think may have caused this larger confidence level?
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Chapter 6 Solutions
Elementary Statistics: Picturing the World (7th Edition)
- Question 2 The data below provides the battery life of thirty eight (38) motorcycle batteries. 100 83 83 105 110 81 114 99 101 105 78 115 74 96 106 89 94 81 106 91 93 86 79 103 94 108 113 100 117 120 77 93 93 85 76 89 78 88 680 a. Test the hypothesis that mean battery life is greater than 90. Use the 1% level of significance. b. Determine if the mean battery life is different from 80. Use the 10% level of significance. Show all steps for the hypothesis test c. Would your conlcusion in part (b) change at the 5% level of significance? | d. Confirm test results in part (b) using JASP. Note: All JASP input files and output tables should be providedarrow_forwardSuppose that 80% of athletes at a certain college graduate. You randomly select eight athletes. What’s the chance that at most 7 of them graduate?arrow_forwardSuppose that you flip a fair coin four times. What’s the chance of getting at least one head?arrow_forward
- Suppose that the chance that an elementary student eats hot lunch is 30 percent. What’s the chance that, among 20 randomly selected students, between 6 and 8 students eat hot lunch (inclusive)?arrow_forwardBob’s commuting times to work are varied. He makes it to work on time 80 percent of the time. On 12 randomly selected trips to work, what’s the chance that Bob makes it on time at least 10 times?arrow_forwardYour chance of winning a small prize in a scratch-off ticket is 10 percent. You buy five tickets. What’s the chance you will win at least one prize?arrow_forward
- Suppose that 60 percent of families own a pet. You randomly sample four families. What is the chance that two or three of them own a pet?arrow_forwardIf 40 percent of university students purchase their textbooks online, in a random sample of five students, what’s the chance that exactly one of them purchased their textbooks online?arrow_forwardA stoplight is green 40 percent of the time. If you stop at this light eight random times, what is the chance that it’s green exactly five times?arrow_forward
- Linear Algebra: A Modern IntroductionAlgebraISBN:9781285463247Author:David PoolePublisher:Cengage Learning
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