96% confidence interval

[logistic_guy]

An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of \(\displaystyle 40\) hours. If a sample of \(\displaystyle 30\) bulbs has an average life of \(\displaystyle 780\) hours, find a \(\displaystyle 96\%\) confidence interval for the population mean of all bulbs produced by this firm.

 

[khansaheb]

An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of \(\displaystyle 40\) hours. If a sample of \(\displaystyle 30\) bulbs has an average life of \(\displaystyle 780\) hours, find a \(\displaystyle 96\%\) confidence interval for the population mean of all bulbs produced by this firm.

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