Reference no: EM131214276
1. Liquid chromatography was used to measure the concentration of caffeine in coffee. The caffeine standards used to make the calibration curve ranged from 2 ppm to 20 ppm. Analysis of the coffee sample using the curve yielded a concentration of 32 ppm.
a. Why would you not be able to use this concentration in your report?
b. What can be done in this circumstance to ensure the method and reported value is valid?
2. Why is it desirable to use a small volume of concentrated standard rather than a large volume of diluted standard in the method of standard addition?
So that the matrix is similar or nearly the same for all solutions measured.
3. Explain the difference between systematic and random error. Give three examples for sources of systematic error.
Systematic errors in experimental observations usually come from the measuring instruments.
Systematic error is a series of errors in accuracy that are consistent in a certain direction and they usually come from the measuring instruments, while random errors are those which are caused by random and unpredictable variation in an experiment.
Examples of causes of systematic errors
• Faulty Instruments (Instrumental) - there is something wrong with the instrument or its data handling system.
• Observational - Wrong use or handling of the instruments by the experimenter or when the observer records a wrong reading
• Environmental - When problems in the lab surrounding lead to inaccurate results..
4. The carbohydrate content of a glycoprotein is found to be 12.6, 11.9, 13.0, 12.7, and 12.5 wt% in replicate analyses. Find the 90% and 99% confidence intervals for the carbohydrate content.
5. A standard reference material is certified to contain 51.1 ppm bismuth. Your analysis gives values of 53.1, 52.9, 53.7, 50.0, and 54.2 ppm. Do your results differ from the expected result at the 95% confidence level? (4 marks)
6. The concentration of HCl in a solution was measured by titrating with different indicators to find the endpoint.
(a) Is the difference between indicators 1 and 2 significant at the 95% confidence interval? (3 marks)
(b) What about the difference between indicators 2 and 3? (4 marks)
Hint: using 40 degrees of freedom for each →Ftable = 2.2 and ttable= 2.02
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Indicator
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Mean HCl concentration (M)
(± standard deviation)
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Number of Measurements
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1. Bromothymol blue
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0.09565 ± 0.00225
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28
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2. Methyl red
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0.08686 ± 0.00098
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18
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3. Bromocresol green
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0.08641 ± 0.00113
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29
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What is true about group iv compared to group iii hydroxides
: A solution contains either Ba2+ or Ca3+. What test could be used to determine the identity of the cation? What is true about the Group IV hydroxides compared to the group III hydroxides?
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Failure statistics department
: In how many ways can we select a committee to develop a reliability program if the committee is to consist of 3 members from the condition monitoring department and 4 members from the failure statistics department?
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Calculate the p-value of the test
: Based on 112 observations in the table, will the hyper geometric distribution an appropriate model to represent these data? Solve the problem with you using a traditional method α of 0.05. In addition, calculate the p-value of the test.
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Perform hypothesis test using
: 1. Perform hypothesis test using α = 0.05. 2. When the test of hypothesis with a fixed level of significance (α = 0.05) has the disadvantage that the researcher truly does not know how far or how close is the value of the test statistic in the cri..
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Explain the difference between systematic and random error
: What can be done in this circumstance to ensure the method and reported value is valid? Explain the difference between systematic and random error. Give three examples for sources of systematic error.
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Draw a neat sketch of the voice and data cabling arrangement
: A building you plan to use as an office has four floors; each floor is a rectangle 1000 ft. long and 300 ft. wide. The vertical separation between the floors is 20 ft. Draw a neat sketch of the voice and data cabling arrangement on any one floor o..
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Hypothesis testing for two populations
: TNH Industry Human Resources department is concerned about the perception of the hours worked per week at the India facility compared to hours worked at the China facility. Sunila, the HR Manager has asked for your help.
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Conduct hypothesis tests for price and proportion
: 1. Conduct hypothesis tests for price and proportion. 2. Based on this updated data and Larry's parameters, should the new line be marketed? Explain your answer.
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Calculate karl pearsons coefficient or correlation
: Calculate Karl Pearson's Coefficient or correlation for the following data relating to overhead expenses and cost of production - Calculate Product moment Coefficient of correlation for the data.
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