Empirical probability is computed by running an experiment multiple times (in this case, asking the same question to many people), and then computing the ratio
[tex]\dfrac{\text{good cases}}{\text{all cases}}[/tex]
In this case, 236 people over 991 said that they checked the portfolio daily, so the empirical probability is
[tex]P(\text{daily check})=\dfrac{236}{991}[/tex]
Which you can round as 0.238, i.e. 23.8%.
