SOCR EduMaterials Activities Discrete Probability examples

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*<math> P(X \ge 1)= 1-P(X=0)=1-.7^8 </math>
*<math> P(X \ge 1)= 1-P(X=0)=1-.7^8 </math>
*<math> Expected value= np = 8*.3=2.4 </math>
*<math> Expected value= np = 8*.3=2.4 </math>
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*<math> Sd(X)= sqrt(np 1-p)</math>
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*<math> Sd(X)= sqrt(npq)</math>

Revision as of 18:43, 23 April 2007

Find the probability that 3 out of 8 plants will survive a frost, given that any such plant will survive a frost with ptobability of 0.30. Also, find the probability that at least 1 out of 8 will survive a frost. What is the expected value and standard deviation of the number of plants that survive the frost?

  • Answer:
  • X \sim b(8,0.3) , P(X=3)= {8 \choose 3} 0.8^30.7^5
  • P(X \ge 1)= 1-P(X=0)=1-.7^8
  • Expectedvalue = np = 8 * .3 = 2.4
  • Sd(X) = sqrt(npq)
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