Analytical Chem Lab Report
I. Introduction:
Measurement is the collection of quantitative data. The proper handling and interpretation of measurements are essential in chemistry and in any scientific endeavor. To use measurements correctly, we must recognize that measurements are not numbers. They always contain a unit and some inherent error.
We define precision as to how well experimental data and values agree with each other in multiple tests. Another important concept when dealing with measurements is accuracy, which refers to the agreement between experimental data and a known value. These two concepts are important when relating to any experimental measurement that we would make. In this experiment, we focus on precision and determine how it varies with different measurements. We need to keep in mind that data can be very precise such that each data point is close to the others, yet contain a high degree of experimental error.
There are quantitative measures of precision, the mean, standard deviation and coefficient of variation to name a few. By definition, mean is the sum of the values of a group of items divided by the number of such items. The standard deviation is a statistical measure of the precision for a series of repetitive measurements. The advantage of using standard deviation is to quote uncertainty in a result is that it has the same units as the mean value. The coefficient of variation is useful for comparing the uncertainty between different measurements of varying absolute magnitude. The coefficient of variation is calculated from the standard deviation and is commonly expressed as percentage (%). These measures of precision are used to be able to determine the variability of spread of data and how precise the results are.
II. Objective:
To determine how precision varies with different measurements.
III. Materials
1 pc ten peso coin Analytical Balance Rubber band
1 pc five peso coin Triple Beam balance Graduated Cylinder
2 pcs one peso coin
Measurement is the collection of quantitative data. The proper handling and interpretation of measurements are essential in chemistry and in any scientific endeavor. To use measurements correctly, we must recognize that measurements are not numbers. They always contain a unit and some inherent error.
We define precision as to how well experimental data and values agree with each other in multiple tests. Another important concept when dealing with measurements is accuracy, which refers to the agreement between experimental data and a known value. These two concepts are important when relating to any experimental measurement that we would make. In this experiment, we focus on precision and determine how it varies with different measurements. We need to keep in mind that data can be very precise such that each data point is close to the others, yet contain a high degree of experimental error.
There are quantitative measures of precision, the mean, standard deviation and coefficient of variation to name a few. By definition, mean is the sum of the values of a group of items divided by the number of such items. The standard deviation is a statistical measure of the precision for a series of repetitive measurements. The advantage of using standard deviation is to quote uncertainty in a result is that it has the same units as the mean value. The coefficient of variation is useful for comparing the uncertainty between different measurements of varying absolute magnitude. The coefficient of variation is calculated from the standard deviation and is commonly expressed as percentage (%). These measures of precision are used to be able to determine the variability of spread of data and how precise the results are.
II. Objective:
To determine how precision varies with different measurements.
III. Materials
1 pc ten peso coin Analytical Balance Rubber band
1 pc five peso coin Triple Beam balance Graduated Cylinder
2 pcs one peso coin
References: Tissue, Brian M. (1995). Analytical Chemistry. The Chemistry Hypermedia Project , from http://www.files.chem.vt.edu/chem-ed/index.html Sauro, Jeff (2004)