Keeping water supplies clean requires regular measurement of levels of pollutants. The measurements are indirect. A typical analysis involves forming a dye by a chemical reaction with the dissolved pollutant, then passing light through the solution and measuring its "absorbance." To calibrate such measurements, the laboratory measures known standard solutions and uses regression to relate absorbance and pollutant concentration. This is usually done every day. The table provided contains one series of data on the absorbance for different levels of nitrates. Nitrates are measured in milligrams per liter of water. Nitrates 50 50 100 200 400 800 1200 1600 2000 2000 Absorbance 7.0 7.5 12.8 24.0 47.0 93.0 138.0 183.0 230.0 226.0 To access the complete data set, click the link for your preferred software format: Excel Minitab JMP SPSS TI R Mac-TXT PC-TXT CSV CrunchIt! (a) Chemical theory says that these data should lie on a straight line. If the correlation is not at least 0.997, something went wrong and the calibration procedure is repeated. Plot the data and find the correlation using the software of your choice or a calculator. (Enter your answer rounded to four decimal places.) r= Must the calibration be done again? yes (b) The calibration process sets nitrate level and measures absorbance. Once established, the linear relationship will be used to estimate the nitrate level in water from a measurement of absorbance. What is the equation of the line used for estimation? Oy= -1.657 - 0.1133x. Oj= -14.52 + 8.825x. O y= -14.52 - 8.825x Oy = 1,657 + 0.1133x. Based on the equation exactly as it appears in your choice in the previous question, to avoid roundoff error, what is the estimated nitrate level in a water specimen with absorbence 40? (Enter your answer rounded to one decimal place.) estimated nitrate level = Oy=-14.52 + 8.825x. O y = -14.52 - 8.825x. O y = 1.657 + 0.1133x Based on the equation exactly as it appears in your choice in the previous question, to avoid roundoff errors, what is the estimated nitrate level in a water specimen with absorbence 40? (Enter your answer rounded to one decimal place,) estimated nitrate level (c) Do you expect estimates of nitrate level from absorbance to be highly accurate? Why? No. This prediction should not be at all accurate because the relationship is so strong. Yes. This prediction should be very accurate because the relationship is so strong. No. This prediction should not be at all accurate because the relationship is relatively weak. Yes. This prediction should be very accurate because the relationship is relatively weak