The above figures are taken from the website of National Stock Exchange of India. They illustrate the movement of NSE stock indices as well as world stock indices on the date indicated.
What do you mean by a stock index?How is it calculated?

Explanation

Stock index refers to the index used to capture the movement of the stock market. It is a barometer which measures overall market trend through a set of stocks which are representatives of the market. An ideal index must represent changes in the prices of securities and also show the price movement of different classes of shares. A stock exchange selects a few most commonly traded shares. Then, the market price of these shares is found out by taking an average of highest price and the lowest price on a day. Then to find out the market capitalisation, the outstanding number of particular shares is multiplied by the price.
Most of the stock market uses the following three methods of calculating stock index:
(i) Price weighted index An index reflecting the sum of the prices of the sample share in a certain year/month/week/day with reference to base year.
(ii) Equal weighted index An index reflecting the simple arithmetic average of the price relatives of a sample of shares in a certain period with reference to base year.
(iii) Value weighted index It is an index reflecting the aggregate market capitalisation of the sample shares in certain period in relation to base year.