def get_t(x, mu, s, n):
    """
    Function to get the T value correspondent of the X value in the t-student
    distribution.
    
    Parameters:
    --------------------------
    x : double, float
        Specific value from the random variable.
    
    mu : double, float
        Population average given.
        
    sd : double, float
        Sample standard deviation given.
        
    n : int, optional
        Sample size, less than 30.
        
    Returns:
    --------------------------
    t : float, double
        The T value correspondent of the X value in the t-student.
    """
    if n > 30:
        print('The sample size must be less than 30.')
    else:
        t = (x - mu) / (s / n ** 0.5)
        return t
