I think your question is if we put a rubber slipper , would it help from getting electric shock. Its not actually the earth you meant. Do you know that electrcity flows from a higher potential to lower potential. Your house is equipped with erath facility to avoid excess electricity to save your home appliances like tv, fridge etc.For electric current there should be a neutral medium to discharge(means lower potential) . Then only the flow completes. Thats why we use earth. Excess current flows through the earth wire to the real earth. When there is no such neutral medium to flow the electric current it will not flow. When we donot have any contact with earth (real earth, that is neutral medium) we will not get electric shock. But the slipper should be thicker. You will get clarified more clearly when you study about electricity in your 11th class.