Computing the Mean

Let's start with an easy one.

The mean (average) of L is $\mu = \sum_{i = 0}^{n-1} L[i]/n$.

We can compute this directly:

int mean( vector<int> & data )
{ 
  int sum = data[0];
  for( int i = 1; i < data.size(); i++ )
    sum += data[i];
  return sum / data.size();
}