Question

A survey of investors finds that 60% use a full service brokerage firm to invest in stocks, 30% trade stocks online and 24% do both. The probability that an investor selected at random uses a full service brokerage firm or trades stocks online is:_______.

a. 90%
b. 66%
c. 34%
d. 54%
e. 60%

Answer 1

`P(Service\ Brokerage\ or\ Online) = 66\%`

Explanation:

Given

`P(Service\ Brokerage) = 60\%`

`P(Online) = 30\%`

`P(Both) = 24\%`

Required

Determine P(Service Brokerage or Online)

In probability:

`P(A\ or\ B) = P(A) + P(B) - P(Both)`

In this case:

`P(Service\ Brokerage\ or\ Online) = P(Service\ Brokerage) + P(Online) - P(Both)`

Substitute values:

`P(Service\ Brokerage\ or\ Online) = 60\% + 30\% - 24\%`

`P(Service\ Brokerage\ or\ Online) = 66\%`

Hence, the required probability is 66%