Question

A utility company might offer electrical rates based on time-of-day consumption to decrease the peak demand in a day. Enough customers need to accept the plan for it to be successful. Suppose that among 50 major customers, 15 would accept the plan. The utility selects 10 major customers randomly (without replacement) to contact and promote the plan. a. What is the probability that exactly two of the selected major customers accept the plan

Answer 1

Answer:

0.2406 = 24.06% probability that exactly two of the selected major customers accept the plan

Step-by-step explanation:

The customers are chosen without replacement, which means that we use the hypergeometric distribution to solve this question.

Hypergeometric distribution:

The probability of x sucesses is given by the following formula:

$P(X = x) = h(x,N,n,k) = \frac{C_{k,x}*C_{N-k,n-x}}{C_{N,n}}$

In which:

x is the number of sucesses.

N is the size of the population.

n is the size of the sample.

k is the total number of desired outcomes.

50 major customers, 15 would accept the plan.

This means that $N = 50, k = 15$

The utility selects 10 major customers randomly (without replacement) to contact and promote the plan.

This means that $n = 10$

a. What is the probability that exactly two of the selected major customers accept the plan

This is P(X = 2).

$P(X = x) = h(x,N,n,k) = \frac{C_{k,x}*C_{N-k,n-x}}{C_{N,n}}$

$P(X = 2) = h(2,50,10,15) = \frac{C_{15,2}*C_{35,8}}{C_{50,10}} = 0.2406$

0.2406 = 24.06% probability that exactly two of the selected major customers accept the plan