In a vase a 10 balls: 4 red and 6 white. They are taken out one by one without replacement.Let X be the stochastic variable that denotes how often we need to draw balls before we draw a white ball.Calculate the probability function of X.

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ambivalentnoe1 · Accepted Answer

Step 1Clearly, X is between 1 and 5. The probability that X equals 1 is the probability of drawing a white ball on the first try, thus       P    (  X  =  1  )  =  6      /    10  =  .6Similarly, the probability that X equals 2 is the probability of drawing first a red ball and then a white ball, thus       P    (  X  =  2  )  =  4      /    10  ×  6      /    9.Step 2The probability that X equals 3 is the probability of drawing first two red balls and then a white ball, that is       P    (  X  =  3  )  =  4      /    10  ×  3      /    9  ×  6      /    8.

In a vase a 10 balls: 4 red and 6 white. They are taken out one by one without replacement. Let X be the stochastic variable that denotes how often we need to draw balls before we draw a white ball. Calculate the probability function of X.

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