Need help with statistics interview question

[Avantika_Sharmaa24]

I'm having trouble with one of the statistics interview questions from this resource. The question is:

Given a data set X, calculate the mean and variance of X.

I've tried to solve the problem using the following code:

Code:

mean = 0
for i in range(len(X)):
    mean += X[i]
mean = mean/len(X)
variance = 0
for i in range(len(X)):
    variance += (X[i]-mean)**2
variance = variance/len(X)

But when I run the code, I get an error. Can anyone help me figure out what the problem is? Any help would be greatly appreciated. Thanks!

[maskaw]

I don't see X defined anywhere