9/9 grades variance wrong, but code same as with others


#1
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:
        variance += ((average - score) ** 2.0)
        variance = variance / float(len(scores))
    return variance
print grades_variance(grades)

def grades_std_deviation(variance):
    return variance ** 0.5
variance = grades_variance(grades)

print grades_std_deviation(variance)

print_grades(grades)
print grades_sum(grades)
print grades_average(grades)
print grades_variance(grades)
print grades_std_deviation(variance)


returns Oops, try again. grades_variance([82, 89, 53, 28, 32, 20, 86, 82, 54, 15, 49, 21]) returned 75.36073615 instead of the correct value 721.2430555556
or similar error regarding wrong value in variance

#2

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 /= len(scores)
return variance

def grades_std_deviation(x):
return x ** 0.5

print print_grades(grades)
print grades_sum(grades)
print grades_average(grades)
print grades_variance(grades)
print grades_std_deviation(grades_variance(grades))


#3

Isn't my code basically the same?


#4

Hi son9o,

This is your vatiance's function

def grades_variance(scores):
    average = grades_average(scores)
    variance = 0
    for score in scores:
        variance += ((average - score) ** 2.0)
        variance = variance / float(len(scores)) #AND HERE IS YOUR PROBLEM.
    return variance

Because, the sentence is into the "for", only need erase this space.


#5

Thanks for your reply, but I still can't see it.


#6

There seems to be a "gotchya" in the code. "Scores" is not defined or populated with anything. Here is how I did it after i figured that out.

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(grades):
    average = grades_average(grades)
    variance = 0
    for score in grades:
        variance += (average - score)**2
        result = variance / len(grades)
    return result
print grades_variance(grades)

def grades_std_deviation(variance):
    return variance ** 0.5
print grades_std_deviation(variance)

print print_grades(grades)
print grades_sum(grades)
print grades_average(grades)
print grades_variance(grades)
print grades_std_deviation(grades_variance(grades))