NBC News reported on May 2, 2013, that 1 in 20 children in the United States have a food allergy of some sort. Consider selecting a random sample of 20 children and let X be the number in the sample who have a food allergy. Then X Bin (20, 0.05). (Round your probabilities to three decimal places.) (a) Determine both P(X S 3) and P(X <3) (b) Determine P(X 2 4) P(X 2 4) - (c) Determine P(1 X3) o) What are E(X) and o? (Round your answers to two decimal places.) E(X) - (e) In a sample of 90 children, what is the probability that none has a food allergy?



Answer :

The P(X = 0) = 0.0769 is the probability that none has a food allergy in the News reported on May 2, 2013, that 1 in 20 children in the United States have a food allergy of some sort.

Here we have;

  • (a) P(X <= three) = 0.9658 , P(X<three) = 0.8728
  • (b) P(X >= 4) = 0.0342
  • (c) P(1 <= X <= three) = 0.6884
  • (d) E(X) = 1.25, sigma(X) = 1.089
  • (e) P(X=0) = 0.0769
  • Step-by-step explanation:
  • We are for the reason that X ~ Bin(25, .05) this means that that this may be approximated as a binomial distribution. The formulation for calculating possibility the use of the binomial distribution is:
  • P(X=x) = "Cx px qn-x
  • wherein n = overall no. of trials
  • x = no. of a hit trials
  • p = possibility of success
  • q = possibility of failure = 1 - p
  • We have n = 25 , p = 0.05 and q = 0.95
  • (a) P(X<=three)= P(X = 0) + P(X = 1) + P(X = 2) +=^ 25 C_ * (0.05) ^ 0 * (0.95) ^ (25 + 0) +^ 25 C 1 (0.05)¹ (0.95)25-1 +25C2 (0.05)² (0.95)25-2 + ^ 25 C_{three} * (0.05) ^ three * (0.95) ^ (25 - three)
  • = 0.2774 + 0.3649 + 0.2305 .
  • 0.09302
  • P(X <= three) = 0.9658
  • P(X < three xss=eliminated xss=eliminated xss=eliminated>
  • =^ 25 C_ * (0.05) ^ 0 * (0.95) ^ (25 + 0) +^ 25 C 1 (0.05)¹ (0.95)25-1 +25C2 (0.05)² (0.95)25-2
  • = 0.2774 + 0.3649 + 0.2305
  • P(X < three>
  • (b P(X >= 4) =1-P(X
  • =1-( P(X = 0) + P(X = 1) + P(X = 2) +
  • P( X = three ))
  • = 1 - 0.9658
  • P(X >= 4) = 0.0342
  • (c) P(1 <= X <= three) = P(X = 1) + P(X = 2) + P(X = three)(0.05)^ 2 (0.95)^ 25-2 +^ 25 C_{three} * (0.05) ^ three * (0.95) ^ (25 - 4)
  • = 0.3649 + 0.2305 +
  • 0.09302
  • P(1 <= X <= three) = 0.6884
  • (d) E(X) = np
  • = (25)(0.05)
  • E(X) = 1.25
  • sigma(X) = sqrt(npq)
  • = sqrt(25) * (0.05)(0.95)
  • sigma(X) = 1.089
  • (e) * n = 50 and p = 0.05 We want P(X = 0) : so,
  • P(X=0)=^ 50 C_ * (0.05) ^ 0 * (0.95) ^ (50 + 0)
  • = (1) ^ * (1)^ * (0.0769)
  • P(X = 0) = 0.0769

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