Screen Link:

https://app.dataquest.io/m/308/measures-of-variability/11/sample-variance-unbiased-estimator

My Code:

Replace this line with your code

```
samples = [[0,3], [0,6],
[3,0], [3,6],
[6,0], [6,3]
]
import numpy as np
def standard_deviation(array):
reference_point = sum(array) / len(array)
distances = []
for value in array:
squared_distance = (value - reference_point)**2
distances.append(squared_distance)
variance = sum(distances) / (len(distances) - 1)
return sqrt(variance)
groupstd = []
groupvar = []
for list in samples:
stdd = standard_deviation(list)
stdvar = standard_deviation(list) ** 2
groupstd.append(stdd)
groupvar.append(stdvar)
smpl_std = (sum(groupstd))/6
smpl_var = (sum(groupvar))/6
pop_var = np.var(population)
pop_std = np.std(population)
equal_stdev = pop_std == smpl_std
equal_var = pop_var == smpl_var
What I expected to happen:
I got no results in output. The exercises in Statistics section are becoming more frustrating. Sometimes I've had to log out of Dataquest and log back in to get an exercise output response. In the case of this example, it stated that my variables were undefined, yet you see in the attached picture and the code above that they were.
What actually happened:
```

Replace this line with the output/error

```
<!--Enter other details below: -->
```