A local firm manufactures LED products that have a lifespan that is approximately normally distributed with a std. dev. of 30 hours. If a sample of 30 LED products has an average lifespan of 780 hours, find a 96\% confidence interval for the population mean of all LED products produced by this firm.

UkusakazaL 2021-08-10 Answered

A local firm manufactures LED products that have a lifespan that is approximately normally distributed with a std. dev. of 30 hours. If a sample of 30 LED products has an average lifespan of 780 hours, find a 96% confidence interval for the population mean of all LED products produced by this firm.
Choose 2 answers in nearest unit (ones) or in whole number.
Example, if your answer is 888.83μ899.56, choose 889 and 900.
775773807797791769789768805763771792

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Answers (1)

question2answer
Answered 2021-08-16 Author has 155 answers

Step 1
It is given that, n=30, x=780 and σ=30
At 96% significance level, the value of z is 2.0537.
Then, the 96% confidence interval is
x±z(σn=780±2.0537(3030)
=780±2.0537(5.4772)
=780±11.2486
=(768.7514, 791.2486)
eq(769, 791) Rounded
Step 2
Therefore, 769 and 791 are the correct options.

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