47.5% of children say that chocolate chip cookie is their favorite kind of cookie. If you randomly select 4 children find the probability that: a) exactly 2 say that chocolate chip cookie is their favorite. c) at least one of the 4 say that chocolate chip cookie is their favorite. d) Find the mean and standard deviation for this sample.

Respuesta :

Answer:

a) 0.3731

b) 0.9241

c) Mean = 1.9

Standard Deviation = 0.9987

Step-by-step explanation:

We are given the following information:

P(chocolate chip cookie) = 47.5% = 0.475

Then the number of children follows a binomial distribution, where

[tex]P(X=x) = \binom{n}{x}.p^x.(1-p)^{n-x}[/tex]

where n is the total number of observations, x is the number of success, p is the probability of success.

Now, we are given n = 4

a) x = 2

We have to evaluate:

[tex]P(x =2)\\= \binom{4}{2}(0.475)^2(1-0.475)^{4-2}\\= 0.3731[/tex]

b) x = 1

We have to evaluate

[tex]P(x \geq 1) = 1 - P(x = 0)\\= 1 - \binom{4}{0}(0.475)^0(1-0.475)^{4-0}\\= 1 - 0.0759\\= 0.9241[/tex]

c) Mean and standard deviation of distribution

[tex]\text{Mean} = np = 4\times 0.475 = 1.9\\\text{Standard deviation} = \sqrt{np(1-p)} = \sqrt{4\times 0.475(1-0.475)} = 0.9987[/tex]