Yes although it's a poorly written question since we're not told whether Tim is classed as a child or a parent
I am tutoring a student. His teacher provided a sample TAKS test with this question.
A census shows that on Tim’s block the families contain 3, 4, 4, 0, 1, 2, 0, 2, 2 children respectively.
If a family on this block is randomly chosen, what is the probability it is Tim’s family?
The correct answer is given as 7/9. 7 - the number of families with children in them; 9 - the total number of families on the block.
But that is the probability of selecting a family with a child. 7 - number of families with children. 9 - total number of families.
The probability of selecting Tim's family from a random selection of families on the block is 1 - number of Tim's families / 9 total number of families (1/9).
I'm double checking. Is 7/9 correct?
Yes what? Is it 7/9 or 1/9?
Even if the question states Tim is a child, there is only 1 desired outcome. Only 1 family contains Tim.
If the question were "Tim is a child. What is the probability of selecting a family that could contain Tim?" then 7/9 would be correct.
But if there is only one desired result, the specific family that contains Tim, then it's either 1/9 or 1/7 (if the problem indicates Tim is a child.)
"I would say 1/7 because Tim is only in one family and there are 7 families with children"
The problem doesn't state Tim is a child.
"I'm assuming all families are equally likely to be chosen. Ideally, this should be part of the problem statement."
The problem states a family is randomly chosen. That means all families are equally likely to be chosen.