# Variance of n discrete time series

I'm currently having problems understanding how to calculate the variance between n given time series, each containing data of exactly one day.

So basically, I'm given one array containing double values (which have at most 4 decimal places) from a specified time interval (granularity of measurements is 30 minutes, which means there are 48 samples a day, defining a time series).

Since the variance needs the probability for each value that may occur (the values reach from 0 to mostly 10, even though all values between 0 to infinity COULD appear, the probability is just very (very) low that the value is greater than 10).

So now I want to ask how to calculate these probabilities for each value, or is there a approximative way (or is it even necessary?).

I'm (obviously) not that advanced in statistics, it is just important in context of a software project.