suyash1989

Population mean is (Total Population / N)

Sample Mean is (Sample/n)

The sample is chosen from the population because you believe it's a good representation of the population. For exam purposes, you will be given the numbers.

The n-1 your referring to is different. You use that denominator when calculating the Covariance when given historical data. The removes the statistical bias. Use that denominator when you see a question in portfolio mgmt asking you to calculate Covariance

Covarance in Quant section uses the probability formula, which is slightly different.

Hope this helps