a) Determine the probability that exactly 2 out of 8

BenoguigoliB

BenoguigoliB

Answered question

2021-09-15

a) Determine the probability that exactly 2 out of 8 randomly selected Americans own a cat.
b) Determine the probability that more than 3 out of 8 randomly selected Americans own a cat.

Answer & Explanation

diskusje5

diskusje5

Skilled2021-09-16Added 82 answers

a) It is given that Veterinary Medical Association states that 30% of Americans own a cat. A sample of 8 Americans is chosen at random. Hence, the sample size (n) will be 8.
Consider that the random variable X represents the number of Americans who own a cat, from the sample of 8 Americans.
Success is defined by a randomly selected American owning a cat. Thus, the probability of success (p) is,
p=P(own a cat)
=30%
=0.30
The binomial probability that exactly 2 out of 8 randomly selected Americans own a cat is represented as P(X=2)=b(8,0.30,2).
Software procedure:
Step-by-step procedure to obtain the required probability using Ti-83 Plus calculator is:
Click on 2nd DISTR.
Select A: binom p df, then press ENTER.
Enter trials: 8,p:0.30, x value:2.
Press Enter.
The output shows the probability as 0.254. Therefore,
P(X=2)=0.254
The probability that exactly 2 out of 8 randomly selected Americans own a cat is 25.4%.
b) The required binomial probability is the probability that more than 3 Americans own a cat. It can be represented as b(9,0.30, more than 3).
The probability can be calculated as:
P(X>3)=1P(X3)
Software procedure:
Step-by-step procedure to obtain the required probability using Ti-83 Plus calculator is:
Click on 2nd DISTR.
Select A: binomcdf, then press ENTER.
Enter trials: 8,p:0.30, x value 3.
Press Enter.
The output shows the probability as 0.8059.
Put the value P(X3)=0.8059 in the above equation.
P(X>3)=1P(X3)
=10.8059
=0.1941.
Therefore, the probability that more than 3 Americans out of 8 randomly selected Americans own a cat is 19.4%.

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