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Posted by on Friday, February 21, 2014 at 11:56am.

Selecting a letter of the alphabet: If 3 letters of the alphabet are selected at random, find the probability of getting at least one letter "x". Letters can be used more than once.

My answer was: P(at least 1 "x) = 1 - (25/26)^3 = 1951/17576 or 0.11

Is this correct?

  • Statistics - , Friday, February 21, 2014 at 12:14pm

    Most problems of the "at least" type are best done by subtracting from total.

    P(at least one x) = 1 - P(no x's) = 1 - (25/26)^3 = 0.111 (3dp)

    So, Yes, you are correct.

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