Question

FRQ 2

At a particular coffee shop, 92% of customers order a beverage, 3% of customers order food alone (order food and not a beverage), and 12% of customers order food and a beverage. Suppose we randomly select a customer. Let B = the customer orders a beverage and F = the customer orders food.


a) What is P(F)? Interpret this value in context.


b) What is the probability that the customer orders food given that they order a beverage? Write this event in symbolic form and find the probability.


c) If 180 customers are randomly selected, how many of them can we expect to order neither food nor a beverage? Justify your response.

Answer 1

a) P(F) = 0.15

b) P(F/B) = 0.13

c) 5% customers order neither food not beverage.

Further explanation is in the explanation section

Explanation:

Solution:

Data given:

B = The customer orders a beverage

F = The customer orders food.

F + B = The customers order food and a beverage.

Percentage share:

F = 3%

B = 92%

F + B = 12%

a)

So, the Probability of B, the customer orders a beverage will be:

P(B) = 92% = 0.92

Probability of (F+B), the customers orders food and beverage will be:

P(F ∩ B) = 12% = 0.12

And we know that, 3% customers order food alone so,

P(F) - P(F ∩ B) = 3% = 0.03

So,

P(F) = (P(F) - P(F ∩ B)) + P(F ∩ B)

P(F) = 0.03 + 0.12

P(F) = 0.15

It means that 15% customer order food only.

b) Probability that the customer orders food given that they order a beverage.

P(F/B) = (Probability that the customer orders food given that they order a beverage.)

P(F/B) = P(F∩B)/P(B)

P(F/B) = 0.12/0.92 = 0.13

P(F/B) = 0.13

Symbolic form of the required probability is = P(F/B)

c) If 180 customers are randomly selected, how many of them can we expect to order neither food nor a beverage?

Probability of ordering food and beverage will be:

P(F U B)

So,

Probability of ordering neither food nor beverage will be = 1 - P(F U B)

And,

P(F U B) = P(F) + P(B) - P(F ∩B)

P(FUB) = 0.15 + 0.92 - 0.12

P(FUB) = 0.95

Probability of ordering neither food nor beverage will be = 1 - P(F U B)

Probability of ordering neither food nor beverage will be = 1 - 0.95

Probability of ordering neither food nor beverage will be = 0.05

Hence, 5% customers order neither food not beverage.

So, we have selected 180 random people so, 5% of 180 =

number of people order neither food nor beverage = 5/100 x 180

number of people order neither food nor beverage = 9 people

It means we can expect out of 180 people, 9 people will not order food or beverage.