Respuesta :
Answer:
0.206 = 20.6% probability that exactly 5 of them weigh more than 20 pounds.
Step-by-step explanation:
For each baby, there are only two possible outcomes. Either they weigh more than 20 pounds, or they do not. The probability of a baby weighing more than 20 pounds is independent of any other baby, which means that the binomial probability distribution is used to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
[tex]P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}[/tex]
In which [tex]C_{n,x}[/tex] is the number of different combinations of x objects from a set of n elements, given by the following formula.
[tex]C_{n,x} = \frac{n!}{x!(n-x)!}[/tex]
And p is the probability of X happening.
A public health organization reports that 30% of baby boys 6 - 8 months old in the United States weigh more than 20 pounds.
This means that [tex]p = 0.3[/tex]
A sample of 15 babies is studied.
This means that [tex]n = 15[/tex]
What is the probability that exactly 5 of them weigh more than 20 pounds
This is P(X = 5). So
[tex]P(X = x) = C_{n,x}.p^{x}.(1-p)^{n-x}[/tex]
[tex]P(X = 5) = C_{15,5}.(0.3)^{5}.(0.7)^{10} = 0.206[/tex]
0.206 = 20.6% probability that exactly 5 of them weigh more than 20 pounds.
