```
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
```

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

**son9o**#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 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))

**darknai**#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.

**johmmlhll**#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))
```