Up-Down Theory

In market some people belive that in same sector one stock goes up another goes down.I observed this is true for Maruti and Mahindra & Mahindra in auto sector.In rice stocks KRBL and REI Agro behaves same way.In IT Sector Infosys and satyam or TCS.So observe these stocks and get benifit. You can earn money by switching between these type of stocks. If you know any stocks like this tell me.