a) Determine the probability that exactly 9 students out of 15 randomly selected

Khaleesi Herbert

Khaleesi Herbert

Answered question

2021-09-24

a) Determine the probability that exactly 9 students out of 15 randomly selected Colorado high school students are graduates.
b) Determine the probability that 8 or fewer students out of 15 randomly selected Colorado high school students are graduates.
c) Determine the probability that at least 9 students out of 15 randomly selected Colorado high school students are graduates.

Answer & Explanation

mhalmantus

mhalmantus

Skilled2021-09-25Added 105 answers

a) According to the given information, the high school graduation rate of Colorado is 75%. A random sample of size (n) 15 is selected. The probability of success (p) is defined as:
p=P (high school student is graduate)
=75%
=0.75
Consider a random variable X which represents the number of Wisconsin high school students who are graduates. Therefore X will follow binomial distribution with parameters 15 and 0.75.
The required binomial probability is the probability that exactly 9 students are graduates. It can be represented by P(x=9)=b(15,0.75,9).
Software procedure:
A step-by-step procedure to obtain the required probability using Ti-83 Plus calculator is:
Click on 2nd DISTR.
Select A: binomp df, then press ENTER.
Enter trials: 15,p:0.75, x value: 9.
Press Enter.
The output shows the probability as 0.092.
Therefore, the probability that exactly 9 students out of 15 randomly selected Colorado high school students are graduates is 9.2%.
b) The required binomial probability is the probability that 8 or fewer students are graduates. It can be represented as:
P(X8)=b (15,0.75,8 or fewer)
Software procedure:
A step-by-step procedure to obtain the required probability using Ti-83 Plus calculator is:
Click on 2nd DISTR.
Select A: binomc df, then press ENTER.
Enter trials: 15,p:0.75, x value: 8.
Press Enter.
The output shows the probability as 0.0562.
Therefore, the probability that exactly 8 or fewer students out of 15 randomly selected Colorado high school students are graduates is 5.7%.
c) The required binomial probability is to determine the probability that at least 9 students are graduates.
The required probability can be calculated as:
P(X9)=1P(X<9)
=1P(X8)
=10.0562
=0.9438
Therefore, the probability that at least 9 students out of 15 randomly selected Colorado high school students are graduates, is 94.3%.

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