Question 4 The life span of a 30-watt LED light is known to be normally distributed with o = 20 hours. A random sample of 20 LED light has a mean life of x = 1020 hours. Compare the 90% confidence...

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Extracted text: Question 4 The life span of a 30-watt LED light is known to be normally distributed with o = 20 hours. A random sample of 20 LED light has a mean life of x = 1020 hours. Compare the 90% confidence lower bound of this confidence interval with a two-sided confidence interval. Which standard normal curve applies to the 90% confidence level? Include your solutions.