A sociologist is studying the relationship within families of the highest educational level achieved. Pairs of brothers, where both are aged between 30 and 50, were investigated. In this group 5% of the elder brothers had primary school education only while 80% had a secondary education and the remainder had some tertiary education. Of those elders who had primary education only, 80% had a younger brother who also had primary education only, while none had a younger brother with tertiary education. Of those elder brothers with secondary education only, 50% had younger brothers who also had secondary level education and 10% had younger brothers with primary education only. 40% of the elder brothers with tertiary education had younger brothers who also had tertiary level education while the remainder had brothers with secondary level education.

Draw up a probability distribution of this situation i.e a list of outcomes and their associated probabilities.

I've looked at examples of this in the textbook I have but I still can't figure out how to do this. I've drawn a tree diagram and calculated the probabilities of all outcomes (as it said in an earlier part of the question which I haven't typed here). Is it not the same thing I've already done? A bit confused here....

Thank you,