I get this error message: `grades_variance([2, 3, 0, 9, 5, 5, 9]) returned 2.6348168083 instead of the expected: 9.9183673469`

.

Where am I getting this wrong?

This is my code:

```
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)
variance = (variance / len(scores)) #I think this is where the error comes from but I'm not sure what should be here.
return variance
print grades_variance(grades)
```