Question

ch 12* here is the probability model for the political affiliation of a randomly chosen adult in the united states.

political affiliation	republican	independent	democrat	other

what is the probability that a randomly chosen american adult is a member of one of the two major political parties (republicans and democrats)?
0.55
0.03
0.97
0.42

Explanation:

Step1: Identify relevant probabilities

The probability of being a Republican is $P(\text{Republican}) = 0.25$ and the probability of being a Democrat is $P(\text{Democrat}) = 0.30$.

Step2: Use addition rule for mutually - exclusive events

Since a person cannot be both a Republican and a Democrat at the same time (mutually - exclusive events), the probability of being a member of one of the two major parties is $P = P(\text{Republican})+P(\text{Democrat})$.
$P=0.25 + 0.30=0.55$

Answer:

0.55