In: Statistics and Probability
Suppose you have a pair of tetrahedra. One is red on one face, yellow on two faces, and green on one face. The other is white and has faces marked 1, 2, 3 ,4
a. Complete the table
1 | 2 | 3 | 4 | |
Red | ||||
Yellow | ||||
Yellow | ||||
Green |
b. If both tetrahedra are tossed, what is the probability of a red (facing down) and a 3 (facing down)? Of a yellow (facing down) and a number >1 on the other (facing down?) Of a green (facing down) and a number >4 (facing down) on the other? Of a yellow (facing down) on the colored one and a sum of >2 of faces showing on the other?
1 | 2 | 3 | 4 | Total | |
Red | 0.0625 | 0.0625 | 0.0625 | 0.0625 | 0.25 |
Yellow | 0.0625 | 0.0625 | 0.0625 | 0.0625 | 0.25 |
Yellow | 0.0625 | 0.0625 | 0.0625 | 0.0625 | 0.25 |
Green | 0.0625 | 0.0625 | 0.0625 | 0.0625 | 0.25 |
Total | 0.25 | 0.25 | 0.25 | 0.25 | 1 |
If both tetrahedra are tossed, what is the probability of a red (facing down) and a 3 (facing down)?
From the above table the P( a red (facing down) and a 3 (facing down) ) = 1/16 = 0.0625
Of a yellow (facing down) and a number >1 on the other (facing down?)
P( a yellow (facing down) and a number >1 on the other (facing down?) )
Let Y = Yellow
Therefore required probability = P( Y, 2) + P( Y, 2 ) + P( Y, 3) + P( Y, 3) + P( Y, 4) + P( Y, 4) = 6*(0.0625) = 0.375
Of a green (facing down) and a number >4 (facing down) on the other?
P( a green (facing down) and a number >4 (facing down) on the other) = 0
Because this is an empty event. ( there is no greater than 4 ).
Of a yellow (facing down) on the colored one and a sum of >2 of faces showing on the other?
P( a yellow (facing down) on the colored one and a sum of >2 of faces showing on the other ) =
Note that P( Yellow) = 8/16 = 0.5
And there are only one posibility of Yellow and sum = 2
So required probability = (8/16) - -(1/16) = 7/16 = 0.4375