The staff requirement is done by the requirement of the 
client, number of  modules , the time given by the client 
so depending on this all we recruit the staff.

Based on the application size, client requirements etc we 
have to estimate the staff requirements...
Assume that application has 5 modules which requires 5 
testers to complete the testing with in 2 months.
but client demands that testing should be completed with in 
one month then the number of resources should be doubled 
i.e. 10 resources should be added to the project to 
complete the assigned task.