To test the quality of the work of a commercial laboratory, duplicate analyses of a purified benzoic acid (68.8% C, 4.953% H) sample were requested. It is assumed that the relative standard deviation of the method is sr →  = 4 ppt for carbon and 6 ppt for hydrogen. The means of the reported results are 68.5% C and 4.882% H. At the 95% confidence level, is there any indication of systematic error in either analysis?

To test the quality of the work of a commercial laboratory, duplicate analyses of a purified benzoic acid (68.8% C, 4.953% H) sample were requested. It is assumed that the relative standard deviation of the method is sr →  = 4 ppt for carbon and 6 ppt for hydrogen. The means of the reported results are 68.5% C and 4.882% H. At the 95% confidence level, is there any indication of systematic error in either analysis?

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 3P

See similar textbooks

Similar questions

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 determination of the corticosteroid methylprednisolone acetate in solutions obtained from pharmaceutical preparations yielded a mean value of 3.7 mg mL with a standard deviation of 0.3 mg mL. For quality control purposes, the relative uncertainty in the concentration should be no more than 3%. How many samples of each batch should be analyzed to ensure that the relative standard deviation does not exceed 9% at the 95% confidence level? samples
9) The following results were obtained in the determination of Vitamin E mass in tablet samples. Sample 1 2 3 4 5 6 Weight of Vitamin E (mg) 249.1 249.9 251.2 250.2 244.8 251.0 i. Determine whether any data should be rejected or not at 90 % confidence level. ii. Calculate the mean and standard deviation of the data set above. ii. Express the mean weight of vitamin C at 99 % confidence interval.
A powder was prepared containing 3.00% NaCN and 97.00% NaCl. A sample obtained from that mixture containing 7.374×10^5 particles weighs 10.0 g. Determine the number and percent relative standard deviation of NaCN particles from a sample of the mixture weighing 6.30 g. I need nNaCN particles and %RSD
A clinical chemist obtained the following data for the alcohol content of a sample of blood: % C2H5OH: 0.084, 0.089, and 0.079. Calculate the 95% confidence interval for the mean assuming that (a) the three results obtained are the only indication of the precision of the method and that (b), from previous experience on hundreds of samples, we know that the standard deviation of the method s 5 0.005% C2H5OH and is a good estimate of s.
A chemical synthesis was carried out four times, resulting in yields of 51.2%,51.2%, 57.4%,57.4%, 48.1%,48.1%, and 44.6%.44.6%. Calculate the range, mean, and average deviation of these values.
[References) A method for the determination of the corticosteroid methylprednisolone acetate in solutions obtained from pharmaceutical preparations yielded a mean value of 3.7 mg mL with a standard deviation of 0.3 mg mL. For quality control purposes, the relative uncertainty in the concentration should be no more than 3%. How many samples of each batch should be analyzed to ensure that the relative standard deviation does not exceed 9% at the 95% confidence level? samples
8) Two different analytical methods are compared for determining Ca. The following are two sets of data. Set 1 Set 2 155.779 155.784 155.787 155.787 155.813 155.765 155.781 155.793 i. i. Determine the mean and the standard deviation in Set 1. Calculate the 95% confidence limit for data in Set 1. Identify a possible outlier in Set 2. Use the Q-test to determine whether it can be retained or rejected at 95% confidence level. ii.
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.
Suppose a certain species of fawns between 1 and 5 months old have a body weight that is approximately normally distributed with mean μ=28.6 kilograms and standard deviation σ=3.7 kilograms. Let x be the weight of a fawn in kilograms. Convert the following z interval to a x interval. 2.7 < z Choices x < 18.61 x < 38.59 x > 38.59 x > 18.61 x -38.59
In replicate analyses, the carbohydrate content of a glycoprotein (a protein with sugars attached to it) is found to be 12.6, 11.9, 13.0, 12.7, and 12.5 g of carbohydrate per 100 g of protein. (a) Find the mean of the measurements. (b) Find the standard deviation (s). (c) Find the 90% confidence intervals for the carbohydrate content. (d) If the mean and s are unchanged, but there are 10 measurements (N=10) instead of 5, what would be the confidence interval? (e) How does increasing the number of replicate measurements affect the reliability of measurements? Explain your answer. (Hint: better precision gives smaller confidence intervals)
Rewrite the number 3.123 56 (+0.167 89%) in the forms (a) number (6absolute uncertainty) and (b) number (+percent relative uncertainty) with an appropriate number of digits.