def degrees_of_freedom(s1, s2, n1, n2):
    """
    Compute the number of degrees of freedom using the Satterhwaite Formula

    @param s1 The unbiased sample variance of the first sample
    @param s2 The unbiased sample variance of the second sample
    @param n1 Thu number of observations in the first sample
    @param n2 The number of observations in the second sample
    """
    numerator = (s1**2/n1 + s2**2/n2)**2
    denominator = ((s1**2/n1)**2)/(n1-1) + ((s2**2/n2)**2)/(n2-1)

    degrees_of_freedom = numerator/denominator

    return degrees_of_freedom