class MoreMath::Sequence

def confidence_interval(alpha = 0.05)

the elements of this Sequence instance as a Range object.
Return the confidence interval for the arithmetic mean with alpha level +alpha+ of 
def confidence_interval(alpha = 0.05)
  td = TDistribution.new(size - 1)
  t = td.inverse_probability(alpha / 2).abs
  delta = t * sample_standard_deviation / Math.sqrt(size)
  (arithmetic_mean - delta)..(arithmetic_mean + delta)
end