Network Perf-Dropped Call

Hi All,

I noticed that different operators or even telcom engineers are having different ways to evaluate network performance from the point of droped calls. Some prefer getting daily total traffics and calculating Drop % by dividing Daily total attempts to total dropped calls, some take only daily total normal seizures and divide it by total drops or some consider only busy hour traffics and Drop/Erlanf rates.
Which way is the best to measure network performance looking only to statistics (Metrica), i need some feedbacks.
Regards