Working on the review and I cannot get this to work. Everything in the last problem worked, but in this problem I can get everything to print but the Std Deviation. Would appreciate any help.

The question:

https://www.codecademy.com/en/courses/python-intermediate-en-7mgOa/2/3?curriculum_id=4f89dab3d788890003000096

The error message:

"Traceback (most recent call last):

File "python", line 39, in

File "python", line 34, in grades_std_deviation

NameError: global name 'scores' is not defined"

When I change "scores" to "grades" I get:

"Oops, try again. grades_std_deviation(755.5) returned 334.0710059172 instead of the correct value 27.4863602538 "

```
Replace this line with your 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
print print_grades(grades)
def grades_sum(grades):
total = 0
for grade in grades:
total += grade
return total
print grades_sum(grades)
def grades_average(grades):
sum_of_grades = grades_sum(grades)
average = sum_of_grades / float(len(grades))
return average
print grades_average(grades)
def grades_variance(scores):
average = grades_average(scores)
variance = 0
for score in scores:
variance += (average - score) ** 2
return variance / float(len(scores))
print grades_variance(grades)
def grades_std_deviation(variance):
variance = grades_variance(scores)
variance ** 0.5
return variance
print grades_std_deviation(grades)
```