ANALYTICAL BIOLOGY ASSIGNMENT ❖ EXERCISE ON WAYS OF DETRMINING PRECISION OF MEASUREMENTS Name :- Cheemala Niteesh Course:- Bs-Biology 1st Year Sign:- 1. Shown in the following rows are results for the determination of acetaminophen or paracetamol (in milligrams) in ten separate tablets of Biogesic R 224.3, 240.4, 246.3, 239.4, 253.1, 261.7, 229.4, 255.5, 235.5, 249.7 Report the mean, range, standard deviation, and variance for these data. Answers:i. Mean = 243.53 ii. Range = 37.6 iii. Standard deviation = √141.27 or 11.885 (approx) iv. Variance = 141.27 2. Salem and Galan have developed a new method for determining the amount of morphine hydrochloride in tablets. Results, in milligrams, for several tablets containing different nominal dosages are as follows: For each dosage, calculate the mean and standard deviation for the milligrams of morphine hydrochloride per tablet. Answers:i. Mean = (sum of all the items)/(number of items) 1. For 100mg dosage = 95.556 2. For 60mg dosage = 55.466 3. For 30 mg dosage = 26.846 4. For 10mg dosage = 12. 323 ii. Standard deviation : 1. For 100mg dosage = √24.682 or 4.968 (approx) 2. For 60mg dosage = √4.447 or 2.108 (approx) 3.For 30mg dosage = √2.699 or 1.642 (approx) 4. For 10mg dosage = √34.045 or 5.834 (approx) 3. A given analytical test was performed five times. The results of the analysis are represented by the following values: 6.738, 6.738, 6.737, 6.739, and 6.738%. Would you say that these results are precise? Can you say that they are accurate? Explain both answers. (Show evidences by providing computations for SD or absolute error, whichever is appropriate). Answers:In the given experiment the results are most accurate and precise. Because when we take 6.738 as true value the other values are close to true value which means the values are most accurate and the values are close to each other irrespective of the true value which means the set of values are precise. Standard deviation = 0 ; mean absolute error = 0 4. A given analytical test was performed five times. The results of the analysis are represented by the following values: 37.23, 32.91, 45.38, 35.22, and 41.81%. Would you say that these results are precise? Can you say that they are accurate? Explain both answers. (Show evidences by providing computations for SD or absolute error, whichever is appropriate). Answers:- In the given experiment the results are inaccurate and imprecise. Because if we take 45.38 as true value the result values are not close to the true value which means the values are inaccurate and the set of result values are not close to each other irrespective of the true value which means the set of values is imprecise. 5. Suppose the correct answer to the analysis represented in number 3 above is 6.923%. What can you say now about the precision and accuracy? Answers:If the true value in 3rd question is 6.923 then the set of values is precise but the values are moderately accurate. Because the set of values are close enough to each other irrespective of the true value which means the set is precise but they are not so close to true value which means they are moderately accurate. 6. A series of eight absorbance measurements using an atomic absorption spectrophotometer are as follows: 0.855, 0.836, 0.848, 0.870, 0.859, 0.841, 0.861, and 0.852. According to the instrument manufacturer, the precision of the absorbance measurements using this instrument should not exceed 1% relative standard deviation. Does it in this case? Answers:-In this case relative standard deviation exceeds 1%. The relative standard deviation in this case is 1.29%
