BUG: Describe is giving me different std.
- [ ] I have checked that this issue has not already been reported.

- [X] I have confirmed this bug exists on the latest version of pandas.

- [X] (optional) I have confirmed this bug exists on the master branch of pandas.

---

**Pandas Version:**
`pandas==1.1.0`

**Data file:** [penguins1@csv](https://observablehq.com/@visnup/hello-danfo-js)

`df.head(10).describe()`

gives me:
![s4](https://user-images.githubusercontent.com/29797787/110579938-b4e1c980-818d-11eb-8bb1-2b6dcdbbeb43.png)

`std` value for `bill_length_mm` is around `2`

`df.head(10)['bill_length_mm'].values
`
result in:
`array([39.1, 39.5, 40.3,  nan, 36.7, 39.3, 38.9, 39.2, 34.1, 42. ])

```
import numpy as np
x = [39.1, 39.5, 40.3,  0, 36.7, 39.3, 38.9, 39.2, 34.1, 42. ]
np.std(x, ddof=1)
```

gives:

`12.445923027240687`

`pd.Series(x).std()` gives `12.445923027240687` (same)

but why describe is giving me `2`??

`
