def METHOD_NAME(a, b):
    assert(len(a) == len(b))
    ma, sa = meansd(a)
    mb, sb = meansd(b)
    r = (1 / (len(a) - 1)) * sum([((a[j] - ma) / sa) * ((b[j] - mb) / sb)
                                  for j in range(len(a))])
    return r