Question

The probability of being a universal donor is 6% (O-negative-blood type). Suppose that 6 people come to a blood drive.' a) What are the mean and standard deviation of the number of universal donors among the 6 people? b) What is the probability that there are exactly three universal donors?

Answer 1

Answer:

$Mean = 0.36$

$SD = 0.5817$

$P(x=3) = 0.003588$

Step-by-step explanation:

Given

Let

A = Event of being a universal donor.

So:

$P(A) = 0.06$

$n = 6$

Solving (a): Mean and Standard deviation.

The mean is:

$Mean = np$

$Mean = 6 * 0.06$

$Mean = 0.36$

The standard deviation is:

$SD = \sqrt{np(1-p)}$

$SD = \sqrt{6*0.06*(1-0.06)}$

$SD = \sqrt{0.3384}$

$SD = 0.5817$

Solving (b): P(x = 3)

The event is a binomial event an dthe probability is calculated as:

$P(x) = ^nC_x * p^x * (1-p)^{n-x}$

So, we have:

$P(x=3) = ^6C_3 * 0.06^3 * (1-0.06)^{6-3}$

$P(x=3) = ^6C_3 * 0.06^3 * (1-0.06)^3$

$P(x=3) = 20 * 0.06^3 * (1-0.06)^3$

$P(x=3) = 0.003588$