Fall 10. Exam1 key

Fall 10. Exam1 key - CHEMISTRY 2101 Fall 2010 Dr. Philippe...

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CHEMISTRY 2101 Name___________________________ Fall 2010 Dr. Philippe Buhlmann Hour Exam I October 8, 2009 Page 1 (1) (30 points in total) Statistics (a) (20 points) A few brief questions: The concentration of glucose in a blood sample was measured and reported along with a 95% confidence interval. Describe briefly the meaning of the confidence interval. The confidence interval is the range of values within which there is a 95% probability of finding the true glucose concentration {or the true mean of the glucose concentration}. Does an increase in the number of measurements decrease the standard deviation? Answer with yes or no; no justification required. No The glucose concentration for the above blood sample was reported as 12.01±0.2049. What problem(s) do you see in this result? How would you report this result? 12.01±0.21 with proper units. A result without units is just as meaningless as a result without indication of the error. Rounding of 0.2049 must be correctly performed to give 0.20. Using a newly purchased instrument that just arrived in the lab yesterday, Peter measured the concentration of potassium in a urine sample three times and obtained a relative standard deviation of 18.2%. What should Peter do to make sure that he has an accurate result? Use another instrument or another technique to measure the same sample. Measure a standard sample to confirm that his instrument and method are giving accurate results. Send the sample to another lab for independent analysis. Note that making more measurements will result in a narrower confidence interval, but this will not improve accuracy.
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CHEMISTRY 2101 Name___________________________ Fall 2010 Dr. Philippe Buhlmann Hour Exam I October 8, 2009 Page 2 (b) (10 points) The As content of a sample was determined in four measurements as 3.102%, 3.076%, and 3.030%. What final answer should be
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Fall 10. Exam1 key - CHEMISTRY 2101 Fall 2010 Dr. Philippe...

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