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A Statistics/Probability Question. I'm a bit lost. Please help. Don't care about an answer. Need help getting there.?
A box contains 10 balls numbered 1, 2, . . ., 10. Suppose that two balls are selected at
random without replacement from this box and the numbers on the balls are noted. Find
the probability that the numbers on the two balls differ by 2 or more.
Redo the problem above assuming that the two balls are selected with replacement.
I have a feeling I'm close to an answer for the first question but the "or more" part of it concerns me.
(9-2)/(10 choose 2) is what I have so far.
1 Answer
- M3Lv 76 years ago
1. Unfavorable combos ( two adjacent balls) = 9 (1-2 through 9-10)
so Pr = 1 - [9/10C2] = 1 - 9/45 = 0.8 <----
2. Now, each ball can be chosen twice, so unfavorable ways = 2*9 = 18,
and Pr = 1 - 18/10^2 = 0.82 <------
