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# - Precision and Accuracy - Lab Report Example

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(Name) (Professor) (Subject) (Date) Part A: Discussion In Part A, the determiner of precision is the percentage mean deviation, which is 0.1846%. Differences in terms of precision, no matter how small, depend on a number of factors. However, the first human factor is that no two trials are exactly the same, as different sets of hand movements, different directions as well as different forces are used in order to deliver the liquid out of a pipette (“Sources of Error in Pipetting”)…

## Extract of sample"- Precision and Accuracy"

Download file to see previous pages The determiner of accuracy is the percentage error, which is valued at 0.06%. Some of these include the lack of experience and poor technique, which actually both go together for when there is lack of experience, the immediate result would be poor technique. Poor technique may be attributed to the parallax error, or the failure to put the eye at a level which is aligned properly to the volume mark of the pipette. This means that if one is looking up the pipette, one can see a meniscus placed too high when it appears to align with the volume mark. In the same way, if one is looking down at the pipette, the meniscus will then be too low when it appears to align with the volume mark. In fact, aside from errors in the placement of the eye with reference to the volume mark, lack of experience and poor technique also translate as the failure of properly aligning the meniscus with the volume mark. ...
his means that it would be very hard to control the force by which the solution should be ejected out of the pipette, thus the delivered solution may be slightly more than what is expected. Although there is a standard amount of force when it comes to delivering the solution out of the pipette, the deviation from the standard is brought about by individual differences as no two or three people can exactly deliver the solution out of the pipette using the same amount of force. Besides, this force is too little and is very hard to quantify and estimate physically. Another possible source of error or deviation from the absolute value of the solution is the possibility that the pipette is dirty or the solution is contaminated, thus there is a possibility that tiny droplets of the solution are left on the walls of the pipette resulting in the delivery of too little solution (“Sources of Error in Pipetting”). Moreover, dirt in the pipette, no matter how little, may cause a slight obstruction in the flow of the outgoing solution thus there is also a possibility that the pipette amount of solution is less than what is expected. Another possible source of error or deviation from the absolute or expected value is the possibility of a broken or chipped pipette, no matter how small the break is (“Sources of Error in Pipetting”). Such a break may cause a disruption in the natural flow of the liquid out of the pipette, thus the outgoing solution is also less than the expected amount. Part B: Conclusion The volume delivered by the pipette was calculated to be 9.99+/- 0.02 mL. The slight change of +/- 0.02 mL is due to a number of factors such as differences in time elapsed during transfer of liquid, possible change in temperature, possible change in evaporation rate, lack of ...Download file to see next pagesRead More
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