Measurement Uncertainty 

[Virtual Presenter] Good morning everyone! Today I'm here to discuss Measurement Uncertainty and how it applies to Helen Huang's research. We will take an in-depth look at the critical values for F, question tables, equations for a set of data, and the tolerance of typical laboratory Class A glassware. Let's get started!.

Tutorial Question.

Table 1 at various dqree Freedom (df) Md levels Table 3: Critical Values Of F and 95% confidence levels confidaue I-eve Dqrees of Freedom.

[Audio] In this slide, we will be discussing the uncertainty of typical laboratory class A glassware. We will be examining different apparatus, like pipets, burets and volumetric flasks, and how their tolerances and relative uncertainties can impact the measurement of liquid volume. According to ASTM E297-02, Table 5 outlines the necessary precision for such glasswares. We will explore the relative uncertainties in volume as measured by each of these apparatus, and consider which one would be more precise to use..

[Audio] Data on this slide illustrates the capacity and tolerance of various types of glassware, such as pipets, burettes, and volumetric flasks. The tolerance level of the flask varies with its volume; for instance, a 5 mL flask has a tolerance range of 0.01 to 0.02 mL, and a 250 mL flask has a tolerance of 0.10 mL. Such tolerance levels are essential to guarantee exact quantity of liquids..

[Audio] Measurement uncertainty is a crucial factor to take into account when using laboratory glassware. An instance where the leeway of glassware is contingent on the capacity is pictured. A 5mL pipet has a 0.01mL tolerance, a 10mL burette has a 0.02mL allowance, and a 250mL volumetric flask has a 0.10mL tolerance. This graph highlights how the precision of glassware alters based on its capacity. These leeway values must be taken into account as they have a strong effect on the outcomes..

[Audio] For this calculation, the answer of X is 91. We must consider that for multiplication and division, the uncertain number should be determined by the least significant figure, whereas for addition or subtraction, the uncertain number needs only to take the most decimal place into consideration..

[Audio] "Accurately measuring data is an essential part of any calculation. In this case, we can see that the final answer for our calculation is 8.6, which is the most uncertain of all our numbers. The way we got to this answer was by combining two calculations. First we added the two numbers, 5.34 and 27.789 to get 33.129. However, since the least decimal place is 2, we round up to 33.13. Next, we subtracted 17.2 from 25.76, getting 8.56. The least decimal place here is 1, so we round up to 8.6. This is the final answer, demonstrating the importance of careful measurements when it comes to calculating..

[Audio] In this slide, we see a numerical example demonstrating measurement uncertainty. The calculation shows that the result is 90.74, however, because this calculation is limited to two significant figures, the final answer is 91. This demonstrates how measurement uncertainty can impact numerical results..

Q2B..

[Audio] We can observe from the table that the average lead content of the four Chinese medicinal herbs is 2.17 ppm, and has a standard deviation of 0.41 ppm. Hence, we can assume that there is a margin of 0.41 ppm when it comes to measuring the lead content in the herbs..

[Audio] We will be discussing measurement uncertainty as part of our presentation. We will be looking at an example of a sample of vinegar being pipetted into a volumetric flask and having the volume made up to a specified level. We will use the tolerance of the pipets and burette to calculate the molarity of the original vinegar solution, as well as its concentration in grams per deciliter, estimating the uncertainty of these quantities at the same time. This example will demonstrate how to accurately measure concentrations in an experiment..

[Audio] The table displays the measurement uncertainty of four values, A, B, C, and E, providing their mean and standard deviation. Also displayed is the new mean and standard deviation resulting from rounding to the first uncertain digit. This table illustrates the effects of measurement uncertainty on means and standard deviations calculations..

[Audio] As can be seen in this table, depending on the type of vessel, the measurement uncertainty for a given capacity can differ. For instance, at a capacity of 5mL, a pipet has an uncertainty of 0.01mL, a burette 0.02mL, and a volumetric flask 0.02mL; whereas, at a capacity of 100mL, a pipet has an uncertainty of 0.05mL, a burette 0.10mL, and a volumetric flask 0.08mL. These outcomes demonstrate the value of correctly choosing the appropriate instrument for the needed precision of measurement..

[Audio] The table under discussion provides data about a sample of vinegar, including standard deviations of measurements taken using a 25mL pipette and 250mL volumetric flask, relative standard deviation and the concentration of the sample. It is apparent that the uncertainty of each measurement increases as the volume of the pipette increases. Additionally, it is clear that the concentration of the sample remains constant throughout the neutralization process. Therefore, it can be concluded that accurate measurement leads to precise results..

[Audio] Applying a 10-fold dilution to the vinegar, it was found to be 1.6782 moles per dm3, with a molecular weight of 60.052 g/mol. This corresponds to a molarity of 100.8 g/dm3, with an uncertainty of 0.5 g/dm3. This result is highly accurate, enabling reliable conclusions to be made about the vinegar concentration..

Measurement Uncertainty.

[Audio] Uncertainty in measurement can be difficult to manage. To aid in this process, we have a flowchart which outlines the measurand and the steps taken to break down the overall uncertainty. A cause-and-effect diagram can be employed to identify and analyse the sources of uncertainty from the components. If certain components show correlation, they can be combined as a combined unit. The estimation of uncertainty then involves specifying the measurand and associated parameters..

[Audio] This slide examines a simple example of how to calculate the measurement uncertainty. Specifically, we will look at how to determine the uncertainty associated with the preparation of a calibration standard. In order to calculate the uncertainty, we must understand the sources of variability in the calibration process. This includes things like measuring accuracy, laboratory temperature, and any environmental factors that could affect the results. Once these sources are identified, we can then determine the amount of uncertainty associated with each factor and calculate the total uncertainty for our calibration standard..

[Audio] As businesses become increasingly competitive and technology rapidly advances, it is ever more important to have accurate measurements and understand the associated uncertainty. Fortunately, there are numerous methods available to estimate the uncertainty associated with measurements. One such method is Helen Huang's Measurement Uncertainty. Helen Huang's Measurement Uncertainty helps identify sources of measurement errors, quantify the uncertainty associated with the errors, and use this data to create decisions based on accurate, reliable information. Investing in this technique will allow you to confidently make informed decisions and increase productivity and efficiency..

Figure A 1.4: Uncertainties in Cd Standard preparation Temp Calibration Repeatabi li m(tare) puriW c(Cd) n@ross) A1.4 Step 3: Quantifying the uncertainty components In step 3 the size of each identified potential source of uncertainty is either directly measured, estimated using previous experimental results or derived from theoretical analysis. The purity of the cadmium is given on the certificate as 0.9999 ± Because there is no additional information about the uncertainty value, a rectangular distribution is assumed. To obtain the standard uncertainty u(P) the value of has to be divided by (see Appendix El.l) 0.0001 = 0.000058.

[Audio] Calculating the fourth step in our calculation requires calculating the standard uncertainty associated with a math equation given by 1000.m.P. The intermediate values, the combined standard uncertainties and their relative standard uncertainties are summarized in the table overleaf. Applying these values, the concentration of the calibration standard is calculated to be 1002.7 mg and the uncertainty associated with each component is combined to be a total of 0.9mg. Lastly, a spreadsheet will be used to calculate the uncertainty contribution for cadmium preparation..

[Audio] An example of the preparation of a calibration standard can be seen by taking a high purity metal, such as cadmium, with a concentration of approximately mg 1-1. The metal must first be cleaned to remove any metal-oxide contamination before it is dissolved in nitric acid and diluted in a volumetric flask. The sources of uncertainty should then be identified and quantified using a cause and effect diagram and a table. The combined standard uncertainty for the preparation of a 1002.7 mg l-1 Cd calibration standard is 0.9 mg, shown diagrammatically in Figure A1.2. This example of calibration standard preparation provides important information for measurement uncertainty analysis..

[Audio] The manufactory has stated a specification for this slide which requires a confidence interval. As an example, a 10mL V-flask is specified to be accurate to 10mL +/- 0.2mL with a 95% confidence interval. Moreover, this specification requires a normal distribution..

[Audio] I'm exploring the difference between rectangular and triangular distributions and their impact on uncertainty. A rectangular distribution suggests extreme values are likely to appear, while a triangular distribution suggests extreme values are less likely to appear. As an example, using a 10mL V-flask, the uncertainty with no confidence interval is 0.2/√3 for a rectangular distribution and 0.2/√6 for a triangular distribution. Understanding these differences and their related uncertainty can be important for many calculations..

[Audio] For this slide, I will discuss Measurement Uncertainty in regards to Helen Huang. For a rectangular distribution, the purity of cadmium is given as 0.9999±0.0001, with uncertainty divided by √3. This means the standard deviation of purity of cadmium is 0.0001/ √3. In the case of a triangular distribution, the manufacturer quotes a volume for the flask as 100mL± 0.1mL. The value of uncertainty is given without a confidence level or distribution information, making it difficult to assume extreme values. As a result, the standard uncertainty must be calculated using the triangular distribution, resulting in a standard deviation of 0.1/ √6..

[Audio] When discussing measuring uncertainty, it is important to consider what is being measured: the consistency of a process and its outcome. Measuring uncertainty helps to ensure that the process remains accurate and reliable, which in turn reduces errors and improves the system. Accuracy is therefore critical to effectively measure uncertainty. To gain a better understanding of this, let us take a closer look at how it works..

[Audio] At the end of this presentation, I would like to express my gratitude for your presence here today. Helen Huang's presentation enabled us to gain a comprehensive understanding of the concepts of Measurement Uncertainty and its relevance to our work. I sincerely appreciate your time and attention. Thank you..