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Question

A study of 420,095 Danish cell phone users found that 0.0321% of them developed cancer of the brain or nervous system. Prior to this study of cell phone use, the rate of such cancer was found 0.0340% for those not using cell phones. Use TI-84  Caculator.

27a) Use the sample data to construct s 90% CI estimate of thr percentage of cell phone users who develop cancer of the brain or nervous system.

27b) Do cell phone users appear to have a rate of cancer of the brain or nervous system that is different from the rate of such cancer among those not using cell phones? Why or why not?

Answer 1

Step 1:

(27a)

Total number of Danish cell phone users in the survey are .

The probability of phone users suffered from brain cancer or nervous system . 

Definition of specific confidence interval for a proportion : ,

where is the population proportion.

is the sample proportion.

.

n is the sample size.

is the confidence interval.

Step 2:

for 90 % confidence interval is 1.65.

.

90% of confidence interval for the proportion is

90% of confidence interval for the proportion of 0.0321% Danish phone users suffered from brain cancer or nervous system is .

Step 3:

(27 b) No, it doesn’t appear that cell phone users have a different cancer rate.  Since the 90% confidence interval based on the sample includes the percentage(0.0340%) from the survey taken prior to cell phone use.

Solution:

(27 a)

90% of confidence interval for the proportion of 0.0321% Danish phone users suffered from brain cancer or nervous system is .

(27 b)

No, it doesn’t appear that cell phone users have a different cancer rate.