A titrimetric method for the determination of calcium in limestone was tested by analysis of an NIST limestone containing 30.15% CaO. The mean result of four analyses was 30.26% CaO, with a standard deviation of 0.085%. By pooling data from several analyses, it was established that s   = 0.094% CaO.a. Do the data indicate the presence of a systematic error at the 95% confidence level?b. Do the data indicate the presence of systematic error at the 95% confidence level if no pooled value for s was available?

A titrimetric method for the determination of calcium in limestone was tested by analysis of an NIST limestone containing 30.15% CaO. The mean result of four analyses was 30.26% CaO, with a standard deviation of 0.085%. By pooling data from several analyses, it was established that s   = 0.094% CaO.a. Do the data indicate the presence of a systematic error at the 95% confidence level?b. Do the data indicate the presence of systematic error at the 95% confidence level if no pooled value for s was available?

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter7: Statistical Data Treatment And Evaluation

Section: Chapter Questions

Problem 7.13QAP

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A titrimetric method for the determination of calcium in limestone was tested with the analysis of a NIST limestone containing 30.15% CaO. The mean of the four analyzes is 30.26% CaO with a standard deviation of 0.085%. From the data accumulated from many analyzes, s→ϭ=0.094% CaO was found.a) Do the data indicate the presence of systematic error at the 95% confidence level?b) When a value for ϭ is unknown, do the data show a systematic error at the 95% confidence level?
A method for the detection of morphine is used to generate a calibration curve in which the assay response (y) is plotted versus morphine concentration (x, in mg/L). This gives a straight line with a slope (m) of 0.241 and a y-intercept (b) of 0.011, where y = mx + b. The slope of this line has a standard deviation of ±0.007, and the standard deviation of the intercept is ±0.006. If the sample from an athlete gives a response of 0.506 ± 0.013 in this method, what is the concentration of morphine in the sample and estimated precision of this concentration?
A volumetric calcium analysis on samples of the blood serum of a patient believed to be suffering from a hyperparathyroid condition produced the following data: mmol Ca/L = 3.10, 3.08, 3.28, 3.15, 3.26, 3.12, 3.14, 3.18, 3.25, 3.11, 2.95. Calculate: Mean Standard deviation Coefficient of variation What is the 95% confidence interval for the mean of the data, assuming no prior information about the precision of the analysis? Apply the Q test to the following data sets to determine whether the outlying result should be retained or rejected at the 95% confidence level. ( work on the first measurements according to your case)
Chemistry The levels of an organic pollutant (P) in the groundwater at the perimeter of a plant were a cause for concern. A 10 mL sample of the water was taken and the pollutant was extracted with 95% efficiency using 25 mL of diethyl ether. GC was used to analyse the concentration of P in diethyl ether. A calibration curve was plotted for a series of standards of P which yielded the following results: Peak Area Toluene Conc. (µg/ml) 12,000 2.6 23,700 5.0 35,500 7.7 46,800 9.9 31,250 Sample Determine the concentration of P in ppb in the initial groundwater sample.
Find the standard deviation (if the mass of KHP in three experimental solutions are 0.467,0.48, and 0.48 and the volume of NaOH IN THE exp are 22,29,24 respectively in order to the masses of KHP ) the average molarity of NaOH in each experiment = 5.30x 10^-4 + 4.137x10^-4 + 5.0x10^-4 divided by 3 = 4.81x10^-4 ).
1. A student performed this experiment and obtained the following concentration values: 0.02813 M, 0.02802, and 0.02788 M a. what is the mean concentration? b. what is the standard deviation of these results? 3. how would the following errors affect the concentration of Cl- obtained in question 2b? give your reasoning in each case. a. the student read the molarity of AgNo3 as 0.02104M instead of 0.02014M b. the student was past the endpoint of titration when he took the final buret reading.
As part of an analytical chemistry laboratory course, a student measured the Ca2+ 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 Ca2+concentration (?¯) and standard deviation (?) in parts per million (ppm). Each sample was measured five times (n=5) by each method. Method City-Supplied Drinking Water (?¯±?x¯±s) Well-Supplied Drinking Water (?¯±?x¯±s) FAAS 57.57±0.68 ppm 64.77±0.70 ppm EDTA titration 58.32±0.96 ppm 65.62±0.97 ppm Method Comparison: For each drinking water sample (city and well), compare the Ca2+ content measured by FAAS and EDTA titration. Calculate the ? value for each sample. Do the methods produce statistically different results at the 95% confidence level when measuring the Ca2+content of the city-supplied drinking water? Do the…
The ratio of the number of atoms of the isotopes 69Ga and 71Ga in eight samples from different sources was measured in an effort to understand differences in reported values of the atomic mass of gallium: Sample 69Ga/71Ga Sample 69Ga/71Ga1 1.526 60 5 1.528 942 1.529 74 6 1.528 043 1.525 92 7 1.526 854 1.527 31 8 1.527 93 Find the (a) mean, (b) standard deviation, (c) variance, and (d) stan-dard deviation of the mean. (e) Write the mean and standard deviation together with an appropriate number of significant digits
A 0.1475-M solution of Ba(OH)2 was used to titrate the acetic acid (60.05 g/mol) in a dilute aqueous solution. The following results were obtained. (See attached image)(a) Calculate the mean w/v percentage of acetic acid in the sample.(b) Calculate the standard deviation for the results.(c) Calculate the 90% confidence interval for the mean.(d) (d) At the 90% confidence level, could any of the results be discarded?
A solution is prepared by weighing 5.0000 g of cesium iodide into a 100-mL volumetric flask. The balance used has a precision of 0.2 mg reported as a standard deviation, and the volumetric flask could be filled with a precision of 0.15mL also reported as a standard deviation. What is the estimated standard deviation of concentration (g/mL)?
A sample containing iron is approximately 99.0% w/w Fe. Using ammonia, iron is precipitated as Fe (OH)3 which is ignited to Fe203. (a) What is the gravimetric factor for analyte Fe (AW=55.85 g/mol) and precipitate Fe203 (FW=159.69 g/mol)? (b) What mass of sample is needed to ensure that the Fe203 precipitate would weigh at least 1.00 g?
An analysis of city drinking water for total hardness was done by two students in the laboratory and produced the following results (in ppm CaCO3): Student A: 228.3, 226.4, 226.9, 227.1, and 228.6. Student B: 229.5, 226.1, 230.7, 223.8, and 227.5What is the 95% confidence interval for the mean?