LS4003 Lab Report 1

Topics: Accuracy and precision, Standard deviation, Sample size, Normal distribution, Arithmetic mean / Pages: 3 (579 words) / Published: Dec 9th, 2014
Precision and Accuracy in the Laboratory
Precision – This is a word used to describe the quality; fact or condition of being exact and accurate.(1)
Accuracy – This is a word to describe the quality or state of being correct or precise. (2)

AIM:
The aim of the practical is to assess the accuracy and precision of three types of pipette.
Abstract:
In this experiment, I am going to be assessing the accuracy of a 10ml graduated pipette, a 1ml blowout pipette and a Gilson P1000 automatic pipette. This will be done by measuring a 1ml volume of distilled water into a plastic cup on top of a balance to obtain the weight of water added each time. From this experiment, I hope to broaden my knowledge on the different types of pipettes available and with the results base my conclusion on which if the three is most reliable and accurate.
Method:
1. Starting with a 1ml blowout pipette, deliver 1ml of distilled water into a pre- weighed plastic weighing cup. Re-weigh the cup immediately and obtain the weight of the water by subtraction.
2. Using the same pipette, deliver a further four 1ml volumes in the same cup, weighing after each delivery to obtain the weight of water added each time.
3. Repeat the above operations using the 10ml graduated pipette and the Gilson P1000 automatic pipette.
4. After all of the weights of water have been recorded from each pipette, convert them into units of volume (µl), taking the temperature into consideration.
5. Record all of the units into a table and calculate the mean, standard deviation and the standard error of the mean for each set of results. (3)
Results:
Room Temperature = 24oC
Density of Water = 0.997296
Gilson P1000 - Weight of cup before experiment = 0.9054g

Adding 1ml each time
1.0093g
2.0080g
2.9614g
3.9592g
4.9469g

Mean of results – 1.0093g + 2.0080g + 2.9614g + 3.9592g + 4.9469g = 14.8848g / 5 = 2.97696g
Graduated Pipette –

Weight of cup before experiment = 0.9296g

Adding 1ml each



References: (1) Oxford university press. (2014) Definition of Precision. Available at: http://www.oxforddictionaries.com/definition/english/precision (2) Oxford university press. (2014) Definition of Accuracy. Available at: http://www.oxforddictionaries.com/definition/english/accuracy (3) Weyers J, Reed R, Jones A & Holmes D. (2012) Practical Skills in Biomolecular Sciences, 4th Edition - Pearson

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