if i have 8 essay topics (a,b,c,d,w,x,y,z) and they will be randomly grouped into 2 groups of 4, what is the probability of getting group (a,b,c,d)? I have no clue how to solve this problem can anyone help?
I assume that the 8 essays are split into 2 groups, and one of the groups is given to you. So how many ways are there of giving you any four essays out of 8?
Look this up in a textbook or https://en.wikipedia.org/wiki/Combination It is written 8C4, and scientific calculators have an nCr key or do it in Excel=COMBIN(8,4). There is only one right combination, so the probability is 1 in 8C4.
Another way of looking at it is to allocate a, b, c and d in turn to one of the two groups. The probability that a will go into your set is 4/8. There are now 3 vacancies in your set out of a total of 7 so the probability of getting the b is 3/7, and the c, 2/6 and so on for d. Multiply these all together.
If you are able to choose either group, then the answer is double that.