# Error in quiz week 4

There appears to be an error in week 4 quiz. The formula indicated as correct is not an option.

{moderator edit - quiz question and answer removed}

Yes, they numbered the index values differently in the “answer” than in the actual choices, but the idea is the same: the index of the A value on the RHS is one less than the index of all the other values. But it’s clear that the one you picked is not the correct answer, right? Because your choice uses the same input at each layer.

You have to think about the other choices and there is one that is correct. The other key thing to realize is how the “zero-based” indexing on python for loops works. Try running the following code and watch what happens:

for ii in range(1,4):
print(f"ii = {ii}")

print(f"After loop ii = {ii}")

Here’s what you get:

ii = 1
ii = 2
ii = 3
After loop ii = 3

See what happened there? Here’s another example:

for ii in range(5):
print(f"ii = {ii}")

print(f"After loop ii = {ii}")

Which gives this:

ii = 0
ii = 1
ii = 2
ii = 3
ii = 4
After loop ii = 4