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. )  

Answer 1

P(a person developing cancer of the brain or nervous system), p = 0.000371

Number of people in study, n = 321,324

q = 1-p = 0.999629

Mean number of people to have cancer, = np

= 321,324 x 0.000371

= 119.21

Standard deviation, =

=

= 10.916

Using normal approximation for binomial distribution, P(X < A) = P(Z < (A - )/)

P(106 or fewer cases) = P(X 106)

= P(Z < (106.5 - 119.21)/10.916)

= P(Z < -1.16)

= 0.123

There is no substantial evidence from the study for the claim by media reports that cell phones cause cancer.