class MoreMath::LinearRegression

def slope_zero?(alpha = 0.05)

(with alpha level _alpha_) to be zero.
passed into the constructor of this LinearRegression instance) is likely
Return true if the slope of the underlying data (not the sample data 
def slope_zero?(alpha = 0.05)
  df = @image.size - 2
  return true if df <= 0 # not enough values to check
  t = tvalue(alpha)
  td = TDistribution.new df
  t.abs <= td.inverse_probability(1 - alpha.abs / 2.0).abs
end