Hi, the result of my function is always a little bit off (less than 1)

I would appreciate some help

```
def grades_sum(scores):
total = 0
for score in scores:
total += score
return total
def grades_average(scores):
sum_of_grades = grades_sum(scores)
average = sum_of_grades / len(scores)
return average
def grades_variance(scores):
average = grades_average(scores)
variance = 0
for score in scores:
variance += ((average - score) ** 2)
variance = variance / float(len(scores))
return variance
print(grades_variance(grades))
```