ECO250

Unit 4 In-Class Exercise

1.What is a random variable? Give an example.

Suppose you are shopping online for a new toy for your dog. As you look at the product reviews, you see the following distribution of ratings. Use this table for questions 2-5.

Stars

Frequency

5

9

4

3

3

2

2

1

1

5

2.Sketch a data visualization of the distribution of stars.

3.What is the probability that a randomly chosen reviewer gave the dog toy 3 stars? What is the probability that a randomly chosen reviewer gave the dog toy 3 or fewer stars?

4.Find the expected value for the number of stars.

5.Find the standard deviation of the number of stars.

6.Write down the formula for the binomial distribution. What do n, x, and represent in the formula? What does n! mean?

7.As you shop for dog treats, a seller advertises that 95% of veterinarians recommend their treats. Suppose you randomly choose 10 veterinarians and ask whether they recommend this seller's treats.

a.What is the probability that exactly nine veterinarians in your sample recommend the seller's treats?

b.What is the probability that more than eight veterinarians in your sample recommend the seller's treats?