def average(num_list):
    """
    Returns the average of numbers in a list.
    Returns 0 for an empty list.
    """
    if not num_list:
        return 0
    return sum(num_list) / len(num_list)

def remove_duplicates(num_list):
    """
    Returns a list with duplicate elements removed.
    """
    return list(set(num_list))

def count_greater_occurrences(num_list, threshold):
    """
    Counts the occurrences of elements in a list that is greater than a specific threshold.
    """
    count = 0
    for item in num_list:
        if item > threshold:
            count += 1
    return count
    
def sum_squares(num_list):
    """
    Returns the sum of squares of numbers in a list.
    """
    return sum([num * num for num in num_list])