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If a fair die is rolled 7 times, what is the probability, rounded to the nearest thousandth, of getting at most 2 twos?

Sagot :

avan8

Answer:

0.904

Step-by-step explanation:

Using the binomial distribution, it is found that there is a 0.905 = 90.5% probability of getting at most 2 twos.

For each time the die is rolled, there are only two possible outcomes, either the result is a 2, or it is not. The result on a roll is independent of any other roll, which means that the binomial distribution is used to solve this question.

Binomial probability distribution

[tex]P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}[/tex]

[tex]C_{n,x} = \frac{n!}{x!(n-x)!}[/tex]

The parameters are:

  • x is the number of successes.
  • n is the number of trials.
  • p is the probability of a success on a single trial.

In this problem:

  • The die is rolled 7 times, hence [tex]n = 7[/tex].
  • One out of the 6 sides is a 2, hence [tex]p = \frac{1}{6} = 0.1667[/tex]

The probability is:

[tex]P(X \leq 2) = P(X = 0) + P(X = 1) + P(X = 2)[/tex]

Hence:

[tex]P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}[/tex]

[tex]P(X = 0) = C_{7,0}.(0.1667)^{0}.(0.8333)^{7} = 0.279[/tex]

[tex]P(X = 1) = C_{7,1}.(0.1667)^{1}.(0.8333)^{6} = 0.391[/tex]

[tex]P(X = 2) = C_{7,2}.(0.1667)^{2}.(0.8333)^{5} = 0.235[/tex]

Then:

[tex]P(X \leq 2) = P(X = 0) + P(X = 1) + P(X = 2) = 0.279 + 0.391 + 0.235 = 0.905[/tex]

0.905 = 90.5% probability of getting at most 2 twos.

A similar problem is given at https://brainly.com/question/24863377