An atomic absorption method for the determination of the amount of iron present in used jet engine oil was found from pooling 30 triplicate analyses to have a standard deviation s = 3.6 mg Fe/mL. If s is a good estimate of σ, calculate the 95 and 99% confidence intervals for the result 18.5 mg Fe/mL if it was based on (a) a single analysis, (b) the mean of two analyses, and (c) the mean of four analyses.

An atomic absorption method for the determination of the amount of iron present in used jet engine oil was found from pooling 30 triplicate analyses to have a standard deviation s = 3.6 mg Fe/mL. If s is a good estimate of σ, calculate the 95 and 99% confidence intervals for the result 18.5 mg Fe/mL if it was based on (a) a single analysis, (b) the mean of two analyses, and (c) the mean of four analyses.

Appl Of Ms Excel In Analytical Chemistry

2nd Edition

ISBN:9781285686691

Author:Crouch

Publisher:Crouch

Chapter2: Basic Statistical Analysis With Excel

Section: Chapter Questions

Problem 10P

See similar textbooks

Similar questions

A chemist obtained the following data for the percent compound Z in triplicates (n=3) of an insecticide preparation: 7.47, 6.98, and 7.27. Calculate the 90% confidence limit for the mean of the data assuming that only information about the precision of the method is the precision for the three data points. 7.24 ± 0.74% 7.24 ± 0.13% 7.24 ± 0.42% 7.24 ± 0.27%
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
(Standard addition) Tooth enamel consists mainly of the mineral calcium hydroxyapatite, Ca10(PO4)6(OH)2. Trace elements in teeth of archeological specimen provide anthropologists with clues about diet and diseases of ancient people. Student at Dankook University measured the trace element strontium (Sr) in enamel from extracted wisdom teeth by atomic absorption spectroscopy. Solutions were prepared with a constant total volume of 10 mL containing 0.750 mg dissolved tooth enamel plus variable concentrations of added standard Sr. Added Standard Sr (ng/mL=ppb) 0 2.50 5.00 7.50 10.00 Emission Signal 28.0 34.3 42.8 51.5 58.6 (a) Make a graph showing the experimental data and the calculated straight line. (b) Find the concentration of Sr in the tooth ennamel in parts per million = μg/mL.
A spectrophotometric method for the quantitative analysis of Pb2+ in blood has a normal calibration curve for which Sstd=(0.296 ppb−1)×Cstd+0.003. What is the concentration of Pb2+ in a sample of blood if Ssamp is 0.397?
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?
What are the advantages and disadvantages of using external standards in instrumental analysis?
why would you write 13.90 when only two sig figs were given? Where does the extra "precision" come from?
For the determination of iron in used jet engine oil, 30 analyzes with 3 repetitions each were made by atomic absorption method and the standard deviation was found s=2.4 µg Fe/mL. Since this standard deviation value is close to the ϭ value, the iron concentration of 18.5 µg Fe/mL(a) by a single analysis,(b) as the average of the two analyzes,(c) Calculate the 80% and 95% confidence intervals if found as the mean of four analyses.
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…
At what wavelength was Pb determined? What is the slope and y-intercept of the calibration curve? The researcher determined the Pb content of water sample from a river suspected to be contaminated with Pb from a nearby factory by complexing with cyanidine and the absorbance measured was 0.405. What is the lead content of the water sample?
You have measured the blank for a determination of arsenic in food samples by hydride-generation atomic fluorescence spectrometry. The blank values are: 0.23 ppb, 0.14 ppb, 0.16 ppb, 0.28 ppb, 0.18 ppb, 0.09 ppb, 0.10 ppb, 0.20 ppb, 0.15 ppb, 0.21 ppb As. What is the LOD?
A chemist obtained the following data for the percent compound Z in triplicates (n=3) of an insecticide preparation: 7.47, 6.98, and 7.27. Calculate the 90% confidence limit for the mean of the data assuming that only information about the precision of the method is the precision for the three data points.