00:01
All right, so we're going to let x be the sum of the faces of a roll of a pair of six -sided die.
00:07
So for a, we want to find the pmf of x.
00:13
So the possible values that x could be would be two, three, four, five, six, seven, eight, nine, ten, eleven, and twelve.
00:29
All right so if we were going to make a table you have x then the probability of x so we want to write down each one of the values that x could be and then the probability of getting said number well the probability of getting a two would be just one -on -one so one out of 36 a three would be one -two or two one so two out of 36 4 would be 3 out of 36 and then 5 would be 4 out of 36 and getting a 6 is 5 out of 36 getting the 7 is 6 out of 36 and then it decreases from there so then for part b it says so suppose that x is 7 or 11 and b is 2 3 or 12 so then use the values in a to calculate the probability of a and probability of b so basically the probability of of x being of seven or x being 11 well probably to x being 7 is just 6 out of 36 then plus probability of being 11 will be 2 at 36 and they have no intersection so 8 out of 36 simplify that to be 4 out of 18 or 2 at a 9 so probability of b, which would be x being 2, 3, or 12, 2, or 3, or 12, well, that would be 1 out of 36 plus a 3, which is 2 at 36, and a 12, which is 1 out of 36...