In [1]:

```
import pandas as pd
```

# Probabilities Add Up to 1¶

Another important property we are going to learn is that *the probabilities of events that make the whole sample space will add up to $1$*. For example:

In [2]:

```
dataset = pd.DataFrame({
'Person #':[1,2,3,4,5,6,7,8,9,10],
'City':['SF','SF','NY','NY','NY','SF','NY','SF','SF','SF'],
'Age':[41,26,28,53,32,51,65,49,25,33]
})
dataset
```

Out[2]:

In [3]:

```
dataset.sample(1)['City'].values[0]
```

Out[3]:

In this experiment, if we think of the events $E=$ "the person chosen is from SF" and $F=$ "the person chosen is from NY", we can notice that toghether they make the whole sample space $\Omega=\{SF,NY\}$.

So, even though we don't know yet how much each probability is, we can tell that: