14. A test has 50 multiple choice questions with 4 possible answers for each que

Question

14. A test has 50 multiple choice questions with 4 possible answers for each question. If you randomly guess at the answers, what is the probability of getting more than 15 answers correct? (6 points) 15. Duracell guarantees their batteries to last at least 10 years in the original package. A random sample of 100 batteries was found to have and average shelf life of 10.4 years witha standard deviation of.6 years? a. Construct a 95% confidence interval for the average shelf life of all Duracell Batteries (6 points) b. Based on your confidence interval, is Duracell safe with their guarantee? (4 points)

Explanation / Answer

Mean is 10.4 and s is 0.6

for sample size of 100, the standard error is SE=s/sqrt(N)=0.6/sqrt(100)=0.06

z for 95% confidence is 1.96

thus lower bound is mean-z*SE=10.4-0.06*1.96=10.2824

upper bound is mean+z*SE=10.4+0.06*1.96=10.5176

Yes it is safe

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