In a study of 321 comma 324 cell phone users, it was found that 106 developed ca
ID: 3370291 • Letter: I
Question
In a study of 321 comma 324 cell phone users, it was found that 106 developed cancer of the brain or nervous system. Assuming that cell phones have no effect, there is a 0.000371 probability of a person developing cancer of the brain or nervous system. We therefore expect about 120 cases of such cancer in a group of 321 comma 324 people. Estimate the probability of 106 or fewer cases of such cancer in a group of 321 comma 324 people. What do these results suggest about media reports that cell phones cause cancer of the brain or nervous system?
(A) P(xl?106 )= ______ ( Round to four decimal places as needed. )
Explanation / Answer
answer is 0.0999
n=321324 ,p=0.000371,mean=np=120(given)
standard deviation=sqrt(np(1-p))=sqrt(321324*0.000371*(1-0.000371))=10.92
here we use standard normal variate z=(x-mean)/sd,
for x=106, z=(x-mean)/sd=(106-120)/10.92=-1.2821
P(x<=106)=P(Z<-1.28)=0.0999
required probability=0.0999