What is Normal Distribution?

When we talk about a distribution, it is simply a collection of scores or raw data. From this data, we can easily calculate the :
Mean: This is simply the average of all of the scores.
Standard Deviation: The standard deviation tells you how much scores tend to differ from the mean. Its a measure of how spread out the scores are.
In Statistics , the Normal distribution or also known as Gaussian Distribution is a continuous probability distribution which tells that how data clusters around the mean or average. Generally the graph plotted is a bell shape , with a peak at the mean. This is always symmetrical with the mean.

What is Index Number and its use

An Index number is a data figure which shows the price or quantity in comparison with the base value. The base value is equals to 100 and it is expressed as 100 times the ratio of the base value.
Index numbers are generally a part of time series analysis where we analyze the trend of values in a group of related variables. Sometimes, Index numbers are also used to compare the geographic areas at a given point of time. Some example of this are Purchasing power parity, consumer price index , cost of living index and retails prices.
A price index is the averages of the prices for a given class of goods or service within a given interval of time.

These index numbers are generally used in seeing the trend and help in formulating the policies.

There are many statistician and mathematician who contributed to calculate the index numbers like Fisher, Laspreys etc.

What is Arithmetic Progression and Geometric Progression ?

In mathematics, arithmetic progression (A.P.) or arithmetic sequence is a series of numbers such that the difference of any two successive members of the sequence is a constant. For instance, the sequence 3, 5, 7, 9, 11, 13... is an arithmetic progression with common difference 2.
If the initial term of an arithmetic progression is a1 and the common difference of successive members is d, then the nth term of the sequence is given by:
An = A1+(n-1) *D

2, 4, 6, 8 ,10 , 12 is a AP series having the common difference of 2.

Geometric progression, also known as a geometric sequence, is a series of numbers each term after the first is found by multiplying the previous one by a fixed non-zero number called the common ratio.
The series can be obtained by :
A, Ar, …………….

2, 4, 8, 16, 32 is a GP series having the common ratio 2

How to calculate Standard Deviation ?

In Statistics , Standard Deviation or S.D. is a measure of the dispersion of a data set. A lower SD indicates that the data points are very close to the mean value and higher SD indicates that the data are spread from the mean value.

The term Standard deviation was coined by Karl Pearson in 1894.

How to calculate the Standard Deviation ?

I- Calculate the mean of the data.
II- Now find out the difference of each data point from the mean.
III- Square all the differences.
IV- Add up all these data and take the square root.
V- You get your standard deviation .
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