SOLUTION: If a quality control manager wants to estimate the average life of light bulbs to within +- 20 hours with a 95%
confidence assuming that the process standard deviation is 100 hour
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-> SOLUTION: If a quality control manager wants to estimate the average life of light bulbs to within +- 20 hours with a 95%
confidence assuming that the process standard deviation is 100 hour
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Question 1170654: If a quality control manager wants to estimate the average life of light bulbs to within +- 20 hours with a 95%
confidence assuming that the process standard deviation is 100 hours,
a) What sample size is needed?
b) What sample size would be needed if the confidence level is increased to 99%?
c) The operations manager purchased two new light bulb production machines from two different vendors
and now wants to determine if there is a difference in the average life expectancy of the bulbs produced by
these two machines. A random sample of 25 light bulbs from machine A indicates a sample mean of 375
hours and a SD of 110 hours, and a similar size random sample from machine B indicates a sample mean of
362 hours and a SD of 125 hours. Using a 0.05 level of significance, is there any evidence of a difference in
the average life of bulbs produced by the two type of machines?
d) What is the p-value of the above test?
Problem 2 (15 points)
It is known that 94% of mice inoculated with the new vaccine are protected from the COVID-19 disease.
a) What is the probability that if 10 mice are inoculated, that at most 2 of the mice contract the disease?
b) Calculate the probability that x out of 1000 inoculated mice contract the disease (x= 1 to 100).
c) Plot the probability P(X=x) versus the number of outcomes of the disease x. What can you observe? Discuss
