#### Statistics

After completion of this chapter, students will be able to:

- know more about the statistics.
- solve the problems related to mean, median and standard deviation.

#### Notes

#### Mean deviation

Mean deviation The average of the absolute values of the deviation of each item from mean, median or mode is known as a mean deviation. Standard deviation Standard deviation is the positive square root of the arithmetic mean of the square of deviations of given data taken from the mean.

#### Standard Deviation

**Standard Deviation**

Standard deviation is the position square root of the arithmetic mean of the squares of the deviations of the given observation from their arithmetic mean.

**Merits and Demerits of Standard Deviation**

**Merits**

- The value of standard deviation is based on each and every item of the data.
- It is free from those defects with which other methods like range, quartile deviation, mean deviation suffer.
- It is less affected by fluctuations of sampling.

**Demerits**

- As compared to the measure, it is somewhat more difficult to understand and compute.
- Its value is unduly affected by extreme observations.