As part of an analytical chemistry laboratory course, a student measured the Ca+ content in two water samples, city-supplied drinking water and well-supplied drinking water, using two different analytical methods, flame atomic absorption spectrometry (FAAS) and EDTA complexometric titration. The results of this experiment are given in the table as the mean Ca+ concentration (x) and standard deviation (s) in parts per million (ppm). Each sample was measured five times (n = 5) by each method. Method FAAS EDTA titration City: tcalc = Method Comparison: For each drinking water sample (city and well), compare the Ca+ content measured by FAAS and EDTA titration. Calculate the t value for each sample. Well: 1 calc = no City-Supplied Drinking Water ( X s) 58.670.57 ppm 59.42 0.97 ppm Do the methods produce statistically different results at the 95% confidence level when measuring the Ca+ content of the city-supplied drinking water? A list of Student's t values can be found in the Student's t table. yes no Well-Supplied Drinking Water ( x s) 64.23 0.58 ppm 65.08 0.99 ppm Do the methods produce statistically different results at the 95% confidence level when measuring the Ca+ content of the well-supplied drinking water? A list of Student's t values can be found in the Student's t table. yes Sample Comparison: For each method (FAAS and EDTA titration), compare the Ca+ content measured in the city-supplied and well-supplied drinking water samples. Calculate the t value for each method. FAAS: EDTA: no Do the drinking water samples contain statistically different amounts of Ca+ at the 95% confidence level when measured by FAAS? A list of Student's t values can be found in the Student's t table. yes tcale = tcale = no Do the drinking water samples contain statistically different amounts of Ca+ at the 95% confidence level when measured by EDTA titration? A list of Student's t values can be found in the Student's t table. yes 5 6 7 8 9 10 11 Degrees of Freedom 50 90 95 98 99 99.5 99.9 1 1.000 6.314 12.706 31.821 2 3 63.656 127.321 636.578 0.816 2.920 4.303 6.965 9.925 14.089 31.598 0.765 2.353 3.182 4.541 5.841 7.453 12.924 0.741 2.132 2.776 3.747 4.604 0.727 2.015 2.571 4 5.598 8.610 3.365 4.032 4.773 6.869 3.143 3.707 4.317 5.959 2.998 3.500 4.029 5.408 0.718 1.943 2.447 0.711 1.895 2.365 0.706 1.860 2.306 0.703 1.833 2.262 2.896 3.355 3.832 5.041 2.821 3.250 3.690 4.781 2.764 3.169 3.581 4.587 0.700 1.812 2.228 0.697 1.796 2.201 2.718 3.106 3.497 4.437 0.695 1.782 2.179 2.681 3.055 3.428 4.318 0.694 1.771 2.160 2.650 3.012 3.372 4.221 2.145 2.624 2.977 3.326 4.140 4.073 0.692 1.761 0.691 1.753 2.131 2.602 2.947 3.252 0.690 1.746 2.120 2.583 2.921 3.252 0.689 1.740 2.110 2.567 2.898 3.222 4.015 3.965 0.688 1.734 2.101 2.552 2.878 3.197 3.922 0.688 1.729 2.093 2.539 2.861 3.174 3.883 0.687 1.725 2.528 2.845 3.153 3.850 2.086 2.060 2.485 2.787 3.078 0.684 1.708 3.725 0.683 1.697 2.042 2.457 2.750 3.030 3.646 3.551 3.460 0.681 1.684 2.021 2.423 2.704 2.971 0.679 1.671 2.000 2.390 2.660 2.915 0.677 1.658 1.980 2.358 2.617 2.860 0.674 1.645 1.960 2.326 2.576 2.807 3.291 Reference: Quantitative Chemical Analysis, Eight Edition, Harris 3.373 Confidence Level (%). 12 13 14 15 16 17 18 19 20 25 30 40 60 120