# Standard Deviation

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Objectives By the end of this lesson you should be able to:

• distinguish between discrete and continuous data.
• calculate the variance for a given set of discrete data.

Prerequisites You should ensure that you have writing material and that you understand mean, frequency and sum as they are used in statistics. Lesson Calculation of variances For discrete variables, variance is calculated using the formula:

Where 'X' are the individual scores,is the mean of the data set and 'n' is the number of values in the data set.