err... statistics thumb of rule... n >= 30 constitute a "large" sample liao.
best answer so far......
i returned that knowledge to teacher already.
My only guess
say 20,000 votes...
max 4 hours count finish also.
y cannot wait for 4 hours meh?
need to have early indication for what?
maybe ..... sample results = 50-49-1 (incumbent-opp-spoilt)
if that happen, ELD will "transfer water" from potong pasir ris, Radin, macP
all the agent + officers all come help after their station finish counting
cos most prob need to re-count
thats my only best explaination if ever why a sample is required.