USA Today reported that about 20% of all people in the United States are illiter

Question

USA Today reported that about 20% of all people in the United States are illiterate. Suppose you take seven people at random off a city street.

(b) Find the mean and standard deviation of this probability distribution. (Round your answers to two decimal places.)

Find the expected number of people in this sample who are illiterate. (Round your answer to two decimal places.)

(c) How many people would you need to interview to be 97% sure that at least seven of these people can read and write (are not illiterate)?

= ___ people = ____ people (a) Make a histogram showing the probability distribution of the number of illiterate people out of the seven people in the sample. 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 23 4 5 6 7 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 23 4 567 0 1 23 4 567

Explanation / Answer

a) for histogram -- top right graph is right

b) = np=7*0.2 =1.4

= (np*(1-p))1/2 =1.06

expected number of people in this sample who are illiterate. =1.4

c)probability of read and right =1-0.2 =0.8

P(X>=7) >0.97

P(X<=6) <0.03

therefore from binomial and hit and trial

people need to be interviewed =12

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