STAT Question

Question

What are the chances that a person who is murdered actually knew the murderer? The answer to this question explains why a lot of police detective work begins with relatives and friends of the victim! About 63% of people who are murdered actually knew the person who committed the murder. Suppose that a detective file in New Orleans has 65 current unsolved murders. Find the following probabilities. (Round your answers to four decimal places.)

 

A at least 35 of the victims knew their murderers

 

B at most 48 of the victims knew their murderers

 

C fewer than 30 victims did not know their murderers

 

D more than 20 victims did not know their murderers

Answer 1

.63 x 65 = about 40.95 victims knew their murderers

P(35 or over knew) = over 50%.

p = .63, q= .37 binomial distribution, n= 65

mean = pn = about 40.95

Var = npq = 40.95(.37)= 15.1515

sd = sqrVar = sqr15.1515 = about 3.8925

z = (35-40.95)/3.8925 = about -1.53

to find P(35+) use z tables or z calculator to find area under the normal curve

from -1.53 <z< +infinity

= about 1