# What is standard deviation and its merits and demerits?

## What is standard deviation and its merits and demerits?

It is rigidly defined and free from any ambiguity. Its calculation is based on all the observations of a series and it cannot be correctly calculated ignoring any item of a series. It strictly follows the algebraic principles, and it never ignores the + and – signs like the mean deviation.

## What are the advantages of mean?

Arithmetic mean is simple to understand and easy to calculate. It is rigidly defined. It is suitable for further algebraic treatment. It is least affected fluctuation of sampling.

## What is meant by mean deviation and state its characteristics?

Mean deviation is the arithmetic average of the deviations of all the values taken from some average value (mean, median, mode) of the series, ignoring signs ( + or - ) of deviations.

## What are the advantages of mean deviation?

Merits of Mean Deviation:

• It is easy to understand mean Deviation.
• Mean Deviation is less affected by extreme value than the Range.
• Mean deviation is based on all the items of the series. It is therefore, more representative than the Range or Quartile Deviation.
• It is very simple and easy measure of dispersion.

## How do you find the sample mean for grouped data?

To calculate the mean of grouped data, the first step is to determine the midpoint (also called a class mark) of each interval, or class. These midpoints must then be multiplied by the frequencies of the corresponding classes. The sum of the products divided by the total number of values will be the value of the mean.

## How do you solve for variance?

How to Calculate Variance

1. Find the mean of the data set. Add all data values and divide by the sample size n.
2. Find the squared difference from the mean for each data value. Subtract the mean from each data value and square the result.
3. Find the sum of all the squared differences. ...
4. Calculate the variance.