The program runs but is not returning the correct answer for 'variance'.

grades = [100, 100, 90, 40, 80, 100, 85, 70, 90, 65, 90, 85, 50.5] def print_grades(grades): for grade in grades: print grade def grades_sum(grades): total = 0 for grade in grades: total += grade return total def grades_average(grades): sum_of_grades = grades_sum(grades) average = sum_of_grades / float(len(grades)) return average def grades_variance(scores): average = grades_average(scores) variance = 0 for score in scores: print variance variance += (average - score)**2 variance /= float(len(scores)) return variance print grades_variance(grades)