3) a) An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 40 hours. If a sample of 30 bulbs has an average life of 780 hours, find a 96% confidence interval for the population mean of all bulbs produced by this firm. b) How large a sample is needed if we wish to be 96% confident that our sample mean will be within 10 hours of the true mean?
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The standard error is calculated as the standard deviation divided by the square root of the sample size. In this case, the standard error is 40/sqrt(30) = 7.3 hours. Show more…
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a) An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 40 hours. If a sample of 30 bulbs has an average life of 780 hours, find a 96% confidence interval for the population mean of all bulbs produced by this firm. b) How large a sample is needed if we wish to be 96% confident that our sample mean will be within 10 hours of the true mean?
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An electric firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 40 hours. a. Find a 96% confidence interval for the population mean μ of all bulbs produced by this firm if a random sample of 30 bulbs has an average life of 780 hours b. How large a sample is needed if we wish to be 96% confident that our sample mean will be within 10 hours of the true mean
Ahmet Y.
An electrical firm manufactures a 100 -watt light bulb, which, according to specifications written on the package, has a mean life of 800 hours with a standard deviation of 50 hours. At most, what percentage of the bulbs fail to last even 700 hours? Assume that the distribution is symmetric about the mean.
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