ESTIMATING THE PRECISION OF PIPET
All measurements contain random errors. Therefore, whenever a measurement is made in the chemistry laboratory, some uncertainty exists. It is desirable to keep this uncertainty as small as possible and obtain measurements that are both precise and accurate. Precision in the laboratory implies that when a series of measurements are taken that they will be close in value to each other. Ideally, our laboratory glassware and instruments will always be as precise as possible. We can estimate qualitatively small undetectable uncertainties producing random error. Random error is cumulative. In this experiment, we will assume that each error has an equal probability of occurring and that each can cause the final result to be high or low by a fixed amount.
In this experiment, you will determine the precision associated with a pipet. Pipets are commonly used in the laboratory to quickly measure or transfer small amounts of liquids. Many pipets are labeled with the uncertainty of the pipet. Replicate measurements using the pipette are recorded on the table provided, this indicates precision of your measurements.
Purpose: The purpose of this experiment is to estimate the precision of a 10-mL pipet through practicing the use of Microsoft Excel manipulation
Result and Data Table:
1. Plot a histogram on Microsoft Excel.
2. Determine the mean, median, standard deviation, maximum, minimum and spread of the data.
3. Comment on the precision. (Hint: Exam the standard deviation)
4. Write and submit a lab report.