What standard deviation it advantages and disadvantages?

Answer 1

Did you mean to ask:

"What is standard deviation, and what are it's advantages and disadvantages" ?

Standard deviation is a measure of how "spread out" a set of data is. If it is large, you have a large range of numbers. If it is small, most of your data points are close to the average.

To find it, you need to subtract the "mean" (average) of the data from each data point, square your answers, add them all together, divide your answer by the number of data points minus 1, and take the square root.

For a better explanation of how to find it, have a look here, see the related link below.

So it's advantage is, it gives you a better picture of your data than just the mean alone. Disadvantages would be that it doesn't tell you the full range of the data, and it can be effected by "outliers" (rare numbers much smaller or larger than everything else in the data set) to give a skewed picture.