Question

At a school's open house, T-shirts and sweatshirts were sold.
Each item was purchased by either a student or a parent.
The two-way frequency table summarizes a random sample of

80

items sold that night.

	Student	Parent
T-shirt	24	19
Sweatshirt	16	21

Let sweatshirt be the event that an item randomly chosen from among those sold was a sweatshirt.

Let student be the event that an item randomly chosen from among those sold was purchased by a student.

Find the following probabilities. Write your answers as decimals.

(a) =P(student) (b) P(sweatshirtand=student) (c) P(sweatshirt|=student)

Answer 1

	Student	Parent	Total
T-shirt	24	19	43
Sweatshirt	16	21	37
Total	40	40	80

a. $P(Student)=\frac{40}{80}=0.5$

b. $P(sweat shirt and Student)=\frac{16}{80}=0.2$

c.

sweatshirt PO student P(SweatshirtandStudent) P(Student) 0.2 0.5 0.4