The mean of a data set is found by adding all numbers in the data set and then dividing by the number of values in the set. Mean is also commonly known as the average. The formula for mean is:

\(𝑚𝑒𝑎𝑛=\frac{∑𝑓𝑥}{∑𝑓}\)

The standard deviation is a measure of the amount of variation or dispersion of a set of values from the mean. The formula is:

\(s.d=\sqrt{\frac{\sum{fx^2}}{\sum f}-\left(\frac{\sum f x}{\sum f}\right)^2}\)

The mean and standard deviation are usually given in the exams. Check with your teachers.

When interpreting mean and standard deviation, keep these points in mind:

• Mean measures overall performance. Depending on the context, a higher mean (such as exam scores) or a lower mean (such as number of defects) may indicate better performance.
• Standard deviation measures how far the data values spread from the mean. A lower standard deviation means the results are more consistent and smaller spread.