7. The variance


#1



7. The variance


It passed me for the lesson but it prints None when I " print grades_variance(grades)"


I expect the variance to be a number.


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 i in scores:
        variance+=(average-i)**2
    variance=variance/len(scores)
    return variance
    
print grades_variance(grades)


#2

it also print 334.071005917, if it doesn't, refresh the page


#3

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