Revision as of 19:31, 24 June 2024 by Admin (Created page with "Suppose we have an urn containing 5 yellow balls and 7 green balls. We draw 3 balls, without replacement, from the urn. Find the expected number of yellow balls drawn. '''References''' {{cite web |url=https://math.dartmouth.edu/~prob/prob/prob.pdf |title=Grinstead and Snell’s Introduction to Probability |last=Doyle |first=Peter G.|date=2006 |access-date=June 6, 2024}}")
Jun 24'24
Exercise
Suppose we have an urn containing 5 yellow balls and 7 green balls. We draw 3 balls, without replacement, from the urn. Find the expected number of yellow balls drawn.
References
Doyle, Peter G. (2006). "Grinstead and Snell's Introduction to Probability" (PDF). Retrieved June 6, 2024.
Jun 26'24
Solution: E
The number of yellows balls drawn has probability distribution:
[[math]]
P(N=k) = \frac{\binom{5}{k} \binom{7}{3-k}}{\binom{12}{3}}.
[[/math]]
Calculating the above gives:
k | P(N=k) |
---|---|
1 | 0.4773 |
2 | 0.3182 |
3 | 0.0455 |
And therefore the expected value equals:
0.4773 + 0.3182*2 + 0.0455*3 = 1.2502