As part of a promotion for a new type of cracker, free trial samples are offered to shoppers in a local supermarket. The probability that a

Question

As part of a promotion for a new type of cracker, free trial samples are offered to shoppers in a local supermarket. The probability that a shopper will buy a packet of crackers after tasting the free sample is 0.200. Different shoppers can be regarded as independent trials. If X is the number among the next 100 shoppers who buy a packet of the crackers after tasting a free sample, then the probability that fewer than 30 buy a packet after tasting a free sample is approximately (Use Normal approximation to solve the problem, if its conditions are met.)

A. 0.2000
B. 0.9938
C. None of the answers are correct.

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Julia 3 weeks 2021-11-08T16:50:09+00:00 1 Answer 0 views 0

Answers ( )

  1. Emma
    0
    2021-11-08T16:51:20+00:00

    Answer:

    The probability that fewer than 30 buy a packet after tasting a free sample is approximately

    B. 0.9938

    Step-by-step explanation:

    We have

    p = 0.2

    q = 1 – 0.2 = 0.8

    n = 100

    and we need to compute P(X<30). First we need to check if normal distribution can be used or not. If np>5 then we can use normal distribution to solve this problem.

    np = 100*0.2 = 20 > 5.

    So we can use the normal approximation to solve this problem.

    μ = np = 20

    σ = √(npq)

      = √(100)(0.2)(0.8)

    σ = 4

    We know that z = (X – μ)/σ, So

    P(X<30) = P[(X-μ)/σ < (30 – μ)/σ]

                  = P(z<(30-20)/4)

                  = P(z < 10/4)

                  = P (z<2.5)

    Using the normal distribution probability table, we get:

    P(z<2.5) = 0.9938

    So, the correct option is B. 0.9938

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