## Statistics: Informed Decisions Using Data (4th Edition)

$0.3$
According to the first Rule for a Discrete Probability Distribution (see page 323): $∑P(x)=1$ $P(3)+P(4)+P(5)+P(6)=1$ $0.4+P(4)+0.1+0.2=1$ $P(4)=1-0.4-0.1-0.2$ $P(4)=0.3$ Notice that: $0\leq P(4)\leq1$ (second Rule)