Concept explainers
During 2012, Texas had listed on FracFocus, an industry fracking disclosure site, nearly 6,000 oil and gas wells in which the fracking methodology was used to extract natural gas. Fontenot et al. (2013) reports on a study of 100 private water wells in or near the Barnett Shale in Texas. There were 91 private wells located within 5 km of an active gas well using fracking, 4 private wells with no gas wells located within a 14 km radius, and 5 wells outside of the Barnett Shale with no gas well located with a 60 km radius. They found that there were elevated levels of potential contaminants such as arsenic and selenium in the 91 wells closest to natural gas extraction sites compared to the 9 wells that were at least 14 km away from an active gas well using the £racking technique to extract natural gas.
- a. Identify the population that is of interest to the researchers.
- b. Describe the sample.
- c. What characteristics of the population are of interest to the researchers?
- d. If the sample measurements are used to make inferences about the population characteristics, why is a measure of reliability of the inferences important?
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Chapter 1 Solutions
An Introduction to Statistical Methods and Data Analysis
- The Department of Natural Resources (DNR) received a complaint from recreational fishermen that a community was releasing sewage into the river where they fished. These types of releases lower the level of dissolved oxygen in the river and hence cause damage to the fish residing in the river. An inspector from the DNR designs a study to investigate the fishermen’s claim. Fifteen water samples are selected at locations on the river upstream from the community and fifteen samples are selected downstream from the community. The dissolved oxygen readings in parts per million (ppm) are given in the following table.Upstream 5.2 4.8 5.1 5.0 4.9 4.8 5.0 4.7 4.7 5.0 4.6 5.2 5.0 4.9 4.7, Downstream 3.2 3.4 3.7 3.9 3.6 3.8 3.9 3.6 4.1 3.3 4.5 3.7 3.9 3.8 3.7 a.In order for the discharge to have an impact on fish health, there needs to be at least a 0.5 ppm reduction in the dissolved oxygen. Do the data provide sufficient evidence that there is a large enough reduction in the mean dissolved oxygen…arrow_forwardAccording to the National Climatic Data Center, San Juan, Puerto Rico, experienced127 days of measurable precipitation(rain) in 1995. This was more days of rain themany of the other weather station reported that year, but it was not considered unusualfor San Juan. By comparison, the situation at Phoenix Arizona, reported 31 days ofprecipitation during the same year (again, not unusual).i. Suppose you were taking a one-day business trip to San Juan. What is theprobability that it will rain while you are there?ii. Suppose you decide instead to take your trip to Phoenix. What is theprobability that measurable precipitations will occur while you are there?arrow_forwardA die was thrown 9000 times and of these 3220 yielded a 3 or 4. Can the die be regarded as unbiased ?arrow_forward
- A state fisheries commission wants to estimate the number of bass caught in a given lake during a season in order to restock the lake with the appropriate number of young fish. The commission could get a fairly accurate assessment of the seasonal catch by extensive “netting sweeps" of the lake before and after a season, but this technique is much too expensive to be done routinely. Therefore, the commission samples a number of lakes and record the seasonal catch (thousands of bass per square mile of lake area) and size of lake (square miles). A simple linear regression was performed and the following R output obtained. Estimate Std. Error t value Pr(>|t|) (Intercept) 2.5463 0.4427 5.7513 0.0000 size 0.0667 0.3672 0.1818 0.8578 If a scatterplot showed a non-linear relationship between the response and explanatory variables, what should be done? O Nothing. Continue the analysis as is. Stop the analysis. Perform a natural log transformation on the response variable first. O Perform a…arrow_forwardA state fisheries commission wants to estimate the number of bass caught in a given lake during a season in order to restock the lake with the appropriate number of young fish. The commission could get a fairly accurate assessment of the seasonal catch by extensive "netting sweeps" of the lake before and after a season, but this technique is much too expensive to be done routinely. Therefore, the commission samples a number of lakes and record the seasonal catch (thousands of bass per square mile of lake area) and size of lake (square miles). A simple linear regression was performed and the following R output obtained. Estimate Std. Error t value Pr(>|t|) (Intercept) 2.5463 0.4427 5.7513 0.0000 size 0.0667 0.3672 0.1818 0.8578 The residual plot is below. Notice how the residuals are randomly scattered for lake sizes up to approximately 0.8 square miles. Which of the following are noticeable in this plot? Check all that apply. Residual Plot 0.5 1.0 1.5 2.0 2.5 size of lake (sq, miles)…arrow_forwardAccording to an article by Hiroko Tabuchi and Michael Corkery, in the New York Times, “Exports of US plastic garbage rise, despite ban.” When more than 180 nations agreed last year to place strict limits on exports of plastic waste from richer countries to poorer ones, the move was seen as a major victory in the fight against plastic pollution. [But,] Data for January showed that exports of scrap plastic from the United States edged upward, to 48 million tons from 45 million tons the previous January. Exports to poorer nations were virtually unchanged from a year ago, totaling 25 million tons. Advocates say that there are clear red flags in the data. Malaysia, which had signed on [to the agreement], remained a major destination for US scrap plastic in January. a. How many pounds did each American contribute on average to the amount of scrap plastic exported from the USA to poorer nations like Malaysia in 2020? Type your work and answer here: b. What was the percent (%) increase in…arrow_forward
- A state fisheries commission wants to estimate the number of bass caught in a given lake during a season in order to restock the lake with the appropriate number of young fish. The commission could get a fairly accurate assessment of the seasonal catch by extensive “netting sweeps" of the lake before and after a season, but this technique is much too expensive to be done routinely. Therefore, the commission samples a number of lakes and record the seasonal catch (thousands of bass per square mile of lake area) and size of lake (square miles). A simple linear regression was performed and the following R output obtained. Estimate Std. Error t value Pr (>|t|) (Intercept) 2.5463 0.4427 5.7513 0.0000 size 0.0667 0.3672 0.1818 0.8578 Predict the seasonal catch for a lake with an area of 2.5 square miles. (Assume 2.5 is within the range of lake areas in the sample.) Round your answer to two decimal places. thousand per square milearrow_forwardA state fisheries commission wants to estimate the number of bass caught in a given lake during a season in order to restock the lake with the appropriate number of young fish. The commission could get a fairly accurate assessment of the seasonal catch by extensive “netting sweeps" of the lake before and after a season, but this technique is much too expensive to be done routinely. Therefore, the commission samples a number of lakes and record the seasonal catch (thousands of bass per square mile of lake area) and size of lake (square miles). A simple linear regression was performed and the following R output obtained. Estimate Std. Error t value Pr(>|t|) (Intercept) 2.5463 0.4427 5.7513 0.0000 size 0.0667 0.3672 0.1818 0.8578 Suppose a natural log transformation on seasonal catch was deemed necessary. Below is the least-squares regression equation: In (ý) = 0.76 + 0.0914x. Predict the seasonal catch for the lake with lake area of 2.5 square miles. Round your answer to one decimal…arrow_forwardAccording to the Pew Research Center, the proportion of the American population who use only a cellular telephone (no landline) is 0.37. Jason conducts a survey of thirty 20- to 24-year-olds who live on their own and finds that 16 do not have a landline to their home. Does this provide sufficient evidence to conclude that the proportion of 20- to 24-year-olds who live on their own and don’t have a landline is greater than 0.37? Use an a=0.10 level of significance. Notearrow_forward
- In recent years more people have been working past the age of 65. In 2005, 27% of people aged 65-69 worked. A recent report from the Organization for Economic Co-operation and Development (OECD) claimed that the percentage working had increased (USA Today, November 16, 2012). The findings reported by the OECD were consistent with taking a sample of 600 people aged 6S-69 and finding that 180 of them were working. a. Develop a point estimate of the proportion of people aged 65-69 who are working (to 2 decimals). b. Set up a hypothesis test so that the rejection of Ho will allow you to conclude that the proportion of people aged 65-69 working has increased from 2005. Họ: P - Select your answer- Ha: p Select your answer - c. Conduct your hypothesis test using a =.05. p-value - Select your answer - What is your conclusion? - Select your answer -arrow_forwardThe Human Toxome Project (HTP) is working to understand the scope of industrial pollution in the human body. Industrial chemicals may enter the body through pollution or as ingredients in consumer products. In October 2008, the scientists at HTP tested cord blood samples for 20 newborn infants in the United States. The cord blood of the "In utero/newborn" group was tested for 430 industrial compounds, pollutants, and other chemicals, including chemicals linked to brain and nervous system toxicity, immune system toxicity, and reproductive toxicity, and fertility problems. There are health concerns about the effects of some chemicals on the brain and nervous system. Table shows how many of the targeted chemicals were found in each infant's cord blood. Construct a 90% confidence interval for the mean number of targeted industrial chemicals to be found in an infant's blood. 79 145 147 160 116 100 159 151 156 137 83 156 94 121 144 123 114 139 117.412 and 137.488 126 99arrow_forwardThe Human Toxome Project (HTP) is working to understand the scope of industrial pollution in the human body. Industrial chemicals may enter the body through pollution or as ingredients in consumer products. In October 2008, the scientists at HTP tested cord blood samples for 20 newborn infants in the United States. The cord blood of the "In utero/newborn" group was tested for 430 industrial compounds, pollutants, and other chemicals, including chemicals linked to brain and nervous system toxicity, immune system toxicity, reproductive toxicity, and fertility problems. There are health concerns about the effects of some chemicals on the brain and nervous system. The table below shows how many of the targeted chemicals were found in each infant's cord blood. 145 159 151 156 126 79 137 147 160 116 100 ... 83 156 94 121 144 123 114 139 99 Use this sample data to construct the 90% confidence interval estimate for the mean number of targeted industrial chemicals to be found in an infant's…arrow_forward
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