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
    """
    #degreeoffreedom= numberofobservation-1
    
    a=s1 /n1
    b=s2 /n2
    c=1/(n1-1)
    d=1/(n2-1)

    degreeoffreedom=(a+b)**2 /( c * a**2 + d * b**2)

    return degreeoffreedom