Let (๐, ๐ ) be a discrete bivariate random vector with joint p.m.f. given by๐๐,๐ (๐ฅ, ๐ฆ) =(๐ ยท ๐ฅ๐ฆ if ๐ฅ โ {1, 2, 3}, ๐ฆ โ {1, 2, 3}0 otherwisewhere ๐ > 0 is an as-of-yet undetermined constant.(a) Find the value of ๐
Question
Let (๐, ๐ ) be a discrete bivariate random vector with joint p.m.f. given by๐๐,๐ (๐ฅ, ๐ฆ) =(๐ ยท ๐ฅ๐ฆ if ๐ฅ โ {1, 2, 3}, ๐ฆ โ {1, 2, 3}0 otherwisewhere ๐ > 0 is an as-of-yet undetermined constant.(a) Find the value of ๐
Solution
To find the value of ๐, we need to use the properties of a probability mass function (p.m.f).
First, we know that the sum of all the probabilities in a p.m.f must equal 1. Therefore, we can set up the equation:
โโ ๐๐,๐ (๐ฅ, ๐ฆ) = 1
Since ๐ and ๐ can take on values from {1, 2, 3}, we can substitute these values into the equation:
๐๐,๐ (1, 1) + ๐๐,๐ (1, 2) + ๐๐,๐ (1, 3) + ๐๐,๐ (2, 1) + ๐๐,๐ (2, 2) + ๐๐,๐ (2, 3) + ๐๐,๐ (3, 1) + ๐๐,๐ (3, 2) + ๐๐,๐ (3, 3) = 1
Substituting the given p.m.f into the equation, we have:
๐ ยท 1 ยท 1 + ๐ ยท 1 ยท 2 + ๐ ยท 1 ยท 3 + ๐ ยท 2 ยท 1 + ๐ ยท 2 ยท 2 + ๐ ยท 2 ยท 3 + ๐ ยท 3 ยท 1 + ๐ ยท 3 ยท 2 + ๐ ยท 3 ยท 3 = 1
Simplifying the equation, we get:
๐(1 + 2 + 3 + 2 + 4 + 6 + 3 + 6 + 9) = 1
๐(36) = 1
Dividing both sides by 36, we find:
๐ = 1/36
Therefore, the value of ๐ is 1/36.
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