Question

example 1: a census was conducted at a university. all students were asked how many tattoos they had. the number of tattoos for each student with each associated probability is given below.
a) what is the prob. that a randomly chosen student has no tattoo?
b) what is the prob. that the student you choose has 1 or more tattoos?
c) what is the prob. that the student you choose has neither 2 nor 3 tattoos?

Explanation:

Step1: Find the probability for part a

The probability that a student has no tattoo is directly given in the table.
$$P(\text{no tattoo}) = 0.85$$

Step2: Find the probability for part b

The probability that a student has 1 or more tattoos is \(1 - P(\text{no tattoo})\).
$$P(1\text{ or more})=1 - 0.85=0.15$$

Step3: Find the probability for part c

The probability that a student has neither 2 nor 3 tattoos is \(1-(P(2)+P(3))\).
$$P(\text{neither 2 nor 3})=1-(0.015 + 0.01)=1 - 0.025 = 0.975$$

Answer:

a) \(0.85\)
b) \(0.15\)
c) \(0.975\)