I've made some improvements, this is my code now:

```
lloyd = {
"name": "Lloyd",
"homework": [90.0, 97.0, 75.0, 92.0],
"quizzes": [88.0, 40.0, 94.0],
"tests": [75.0, 90.0]
}
alice = {
"name": "Alice",
"homework": [100.0, 92.0, 98.0, 100.0],
"quizzes": [82.0, 83.0, 91.0],
"tests": [89.0, 97.0]
}
tyler = {
"name": "Tyler",
"homework": [0.0, 87.0, 75.0, 22.0],
"quizzes": [0.0, 75.0, 78.0],
"tests": [100.0, 100.0]
}
def average(numbers) :
total = sum(numbers)
total = float(total) / len(numbers)
return total
def get_average(student) :
homework = average(student["homework"]) * 0.1
quizzes = average(student["quizzes"]) * 0.3
tests = average(student["tests"]) * 0.6
final_grade = homework + quizzes + tests
return final_grade
def get_letter_grade(score) :
if score >= 90:
return 'A'
elif score >= 80:
return 'B'
elif score >= 70:
return 'C'
elif score >= 60:
return 'D'
else:
return 'F'
#print get_letter_grade(get_average(tyler))
def get_class_average(students):
for student in students:
results.append(get_average(student))
return average(results)
print average[results]
#print get_average([lloyd])
print get_class_average(get_average([lloyd]))
```

Now, the error message I get is:

```
Traceback (most recent call last):
File "python", line 50, in <module>
NameError: name 'results' is not defined
```

This is line 50:

`print average(results)`