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as earnings, dividend announcements, price earnings ratio, information about the economy and political news (Reilly1997). New public information is almost instantaneously integrated in share price and the share price is adjusted so as to reflect the true value of the share. This means that an investor cannot use public information to generate gains on the stock market.

In order to test for semi-strong form efficiency, event studies are often used. These event studies are performed by analyzing the effect of the release of new public information on the share price. If the market is semi-strong form efficient, the new public information ( for example annual reports, earning announcement or dividend announcement) is instantaneously integrated in the share price, so as to reflect the intrinsic value of the share. New information can be both good or bad. Thus they can cause increases or decreases at their release.

2.3.3 Strong Form Efficiency
Under strong form efficiency, the current price reflects all information, public as well as private. Private information, in this context, means information not yet published. On the stock market, there are professionals (for example security analysts, fund managers) who have private as well as public information. Efficient Market Hypothesis (EMH) assumes that no investor has monopolistic access to any information. This means that as new public and private information is released, it is incorporated in share price to reflect its true value. An investor will not be able to consistently find undervalued or overvalued shares and make gains on the strong form efficient market. Fama (1970) perceives a strong form efficient market as one where investors are not expected to earn excess returns by relying on inside information.

To test whether past share prices, public and private information can used to predict future share prices, the investment records and gains generated by professional investors are often studied. Investors should not be consistently able to make gains by using public and private information. At all moments, the share prices incorporate all public and private information to reflect the true value of the shares.

2.4 Statistical Tests to examine validity of Weak-Form EMH
In order to examine the validity of the weak form efficiency, a number of statistical tests have been used in the literature. These tests can be categorized into two groups:

i. Using mechanical trading rules also known as filter rules.

These rules test for the possibility of non-linear dependence existing in the price data. Filter rules were first used by S.A Alexander (1961) and later Fama and Blume (1966) added to the literature. Professor Alexander's filter techniques attempts to apply a sophisticated criteria to identify movements in stock prices. An x percent filter is defined as follows: If the daily closing price of a particular security moves up at least x percent, buy and hold the security until its price moves down at least x percent from a subsequent high, then sell and go short (Fama and Blume, 1966). The short position is then maintained until the daily closing price rises at least x percent above a subsequent low when one is going to cover and buy. Moves less than x percent in either direction are ignored.

ii. Statistical tests of independence between successive price changes.

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