yafch,
What are you meaning by ''amplifier factor/amplification factor of a transistor''?
Maybe you are referring to Current gain of a transistor, so called 'Beta' or 'Hfe'?
The current gain for a transistor when OPERATING is equal to Collector current divided to Base current. If you divide those currents, you will reach a number (it is unitless), the said number tells you the rate of current gain or current amplification of the transistor at that operation point.
For common transistors beta is between 200 to 400 but most designers tend to use a Beta much less than those numbers in their designs.
makes sense?