sat suite question viewer
| – years | – years | years | Total | |
|---|---|---|---|---|
| Group A | ||||
| Group B | ||||
| Group C | ||||
| Total |
The table summarizes the distribution of age and assigned group for participants in a study.
One of these participants will be selected at random. What is the probability of selecting a participant from group A, given that the participant is at least 10 years of age?
Explanation
Choice B is correct. Since the participant will be selected at random, the probability of selecting a participant from group A, given that the participant is at least years of age, is equal to the number of participants from group A who are at least years of age divided by the total number of participants who are at least years of age. Based on the table, in group A, there are participants who are – years of age and participants who are years of age. Therefore, there are a total of , or , participants in group A who are at least years of age. Based on the table, of the total number of participants, there are participants who are – years of age and participants who are years of age. Therefore, a total of , or , of the participants are at least years of age. Thus, the probability of selecting a participant from group A, given that the participant is at least years of age, is , or .
Choice A is incorrect. This is the number of participants from group A who are at least years of age divided by the total number of participants, rather than divided by the number of participants who are at least years of age.
Choice C is incorrect. This is the probability of randomly selecting a participant from group A, given that the participant is – years of age, rather than given that the participant is at least years of age.
Choice D is incorrect. This is the probability of randomly selecting a participant who is at least years of age, given that the participant is in group A.