How does the sample variance differ from the population variance?
Once we know the parameters of the underlying population, the population variance is obtained by the formula which is predefined. For the sample variance, we actually calculate the variance.
Let us consider the simple experiment of tossing a set of 5 coins 25 times. In other words, I give a coin each to 5 students and ask them to toss the coin simultaneously. This is repeated 25 times.
Each time the students toss the coin, it is considered a trial. We have 25 trials to complete the experiment.
If it is assumed that the coins used are fair coins (i.e. a head or tail occurs with equal probability ) , the population variance is obtained as 5 x