Question

Disks of polycarbonate plastic from a supplier are analyzed for scratch and shock resistance. The results from 100 disks are summarized as follows:

shock resistance
scratch resistance high low
high 70 9
low 16 5
Let A denote the event that a disk has high shock resistance, and let B denote the event that a disk has high scratch resistance. If a disk is selected at random, determine the following probabilities. Input your answers in the fractional form (do not simplify).

P(A)
P(B)
P(A')
P(A U B)
P(A' U B)

Answer 1

P(A) = 86/100

P(B) = 79/100

P(A') = 14/100

P(A U B) = 95/100

P(A' U B) = 84/100

Explanation:

i. P(A) = number of disks with high shock resistance/total number of disks

= (70+16)/100

= 86/100

ii. P(B) = number of disks with high scratch resistance/total number of disks

= (70+9)/100

= 79/100

iii. P(A') = number of disks without high shock resistance/total number of disks

= (100-86)/100

= 14/100

iv. P(AUB) = number of disks with high shock resistance or high scratch resistance/total number of disks

= (70+9+16)/100

= 95/100

v. P(A'UB) = number of disks without high shock resistance or with high scratch resistance/total number of disks

= (5+9+70)/100

= 84/100