Airline Satisfaction: A CNN/IJSA - Today/Gallup poll in April 2005 reported that

Question

Airline Satisfaction: A CNN/IJSA - Today/Gallup poll in April 2005 reported that 75% of adult Americans were satisfied with the job the nation's major airlines were doing. Suppose 10 adult Americans arc selected at random and the number who are satisfied is recorded. a) Find the probability that exactly 6 are satisfied with the airline. b) Find the probability that fewer than 7 are satisfied with the airline. c) Find the probability that 5 or more are satisfied with the airline. d) Find the probability that between 5 and 8, inclusive, arc satisfied with the airline.

Explanation / Answer

Here we will use binomial distribution p=0.75 and n=20

1. P(x=6)=ncxpx(1-p)(n-x)=0.146

2. P(x<7)=0.2241

3. P(x>=5)=0.9803

4. P5<x<8)=P(x<8)-P(x<=5)=0.4744-0.0781=0.3963

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