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Unformatted text preview: should be discarded. The following sections describe these procedures.
Average and Standard Deviation
The average or mean, x, is defined by
x= N where each xi is one measurement and N is the number of trials or samples.
The standard deviation, , measures how close values are clustered about the
mean. The standard deviation for small samples is defined by
= (xi - x)2
N-1 The smaller the value of the more closely packed the data is about the mean, or,
in other words, the measurements are more precise.
Confidence limits provide an indication of data precision. For example, a 90%
confidence limit of 2.0 indicates that there is a 90% probability that the true
average of an infinite collection of data is within 2.0 of the calculated average
of a limited collection. Clearly the more precise a set of data, the smaller the
confidence interval. Thus, a small confidence interval is always the goal of any
experiment. In General Chemistry you will be required to calculate the 90%
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This note was uploaded on 04/09/2013 for the course CHE CHE 2C taught by Professor Nasiri during the Spring '07 term at UC Davis.
- Spring '07