def reject_h0(crit_val, value, tail):
    """
    Function to determine if reject the null hypothesis or not reject it based
    on the tail-type test.
    
    Parameters:
    --------------------------
    crit_val : tuple, float
        Critical values to consider.
        
    value : float, double
        Value to compare with critical values.
        
    tail : string
        Tail-type test, it could be 'left', 'right' or 'two'.
        
    Returns:
    --------------------------
    decision : bool
        True if we should reject null hypothesis,
        False if we shouldn't reject null hypothesis.
    """
    if tail == 'two':
        return (value < crit_val[0] or value > crit_val[1])
    
    if tail == 'left':
        return value < crit_val
    
    if tail == 'right':
        return value > crit_val
    
    print("You must input a valid tail ('two', 'left' or 'right')")