Question

how to know when reading a question if that was giving sigma or s?

Answer 1

If we have a given population

From population if we find standard deviation then it is SIGMA

Now

From population we draw a random sample of size n

By using random sample if we find standard deviation then it is " S "

Population Mean = mu

Population standard deviation = sigma

Sample mean = Xbar

Sample standard deviation = s

(Note : in case of formulas

for population standard deviation the denominator is always n

for sample standard deviation the denominator is always n-1 )