The variance!


#1

my code is working fine but still they are not consedring it ryt ! help ! whats wrong in it?

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):
    variance=0
    for score in scores:
       t =(grades_average(grades)-score)**2
       variance+=t
       a=variance/float(len(scores))
     return a
print grades_variance(grades)

#2

this line:

a=variance/float(len(scores))

currently you calculate the variance (a) each iteration of the loop, what you want to do is get the total and then after the loop divided the total by the number of scores (length) to calculate the variance


#3

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