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i only want (d) to be solved the answers in the box are 

5- has or does not have 

6- less than 2 or more than 5 

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The quality control manager at a light bulb factory needs to estimate the mean life of a large shipment of light bulbs. The standard deviation is 126 hours. A random
sample of 81 light bulbs indicated a sample mean life of 400 hours. Complete parts (a) through (d) below.
a. Construct a 95% confidence interval estimate for the population mean life of light bulbs in this shipment.
The 95% confidence interval estimate is from a lower limit of
hours to an upper limit of
hours.
(Round to one decimal place as needed.)
b. Do you think that the manufacturer has the right to state that the light bulbs have a mean life of 460 hours? Explain.
Based on the sample data, the manufacturer
the right to state that the lightbulbs have a mean life of 460 hours. A mean of 460 hours is
standard errors
V the sample mean, so it is
that the lightbulbs have a mean life of 460 hours.
c. Must you assume that the population light bulb life is normally distributed? Explain.
O A. No, since o is known, the sampling distribution of the mean does not need to be approximately normally distributed.
O B. Yes, the sample size is not large enough for the sampling distribution of the mean to be approximately normal by the Central Limit Theorem.
O C. Yes, the sample size is too large for the sampling distribution of the mean to be approximately normal by the Central Limit Theorem.
O D. No, since o is known and the sample size is large enough, the sampling distribution of the mean is approximately normal by the Central Limit Theorem.
d. Suppose the standard deviation changes to 99 hours. What are your answers in (a) and (b)?
The 95% confidence interval estimate would be from a lower limit of
hours to an upper limit of
hours.
(Round to one decimal place as needed.)
Based on the sample data and a standard deviation of 99 hours, the manufacturer
V the right to state that the light bulbs have a mean life of 460 hours.
A mean of 460 hours is
V standard errors
the sample mean, so it is
V that the light bulbs have
mean life of 460 hours
Transcribed Image Text:The quality control manager at a light bulb factory needs to estimate the mean life of a large shipment of light bulbs. The standard deviation is 126 hours. A random sample of 81 light bulbs indicated a sample mean life of 400 hours. Complete parts (a) through (d) below. a. Construct a 95% confidence interval estimate for the population mean life of light bulbs in this shipment. The 95% confidence interval estimate is from a lower limit of hours to an upper limit of hours. (Round to one decimal place as needed.) b. Do you think that the manufacturer has the right to state that the light bulbs have a mean life of 460 hours? Explain. Based on the sample data, the manufacturer the right to state that the lightbulbs have a mean life of 460 hours. A mean of 460 hours is standard errors V the sample mean, so it is that the lightbulbs have a mean life of 460 hours. c. Must you assume that the population light bulb life is normally distributed? Explain. O A. No, since o is known, the sampling distribution of the mean does not need to be approximately normally distributed. O B. Yes, the sample size is not large enough for the sampling distribution of the mean to be approximately normal by the Central Limit Theorem. O C. Yes, the sample size is too large for the sampling distribution of the mean to be approximately normal by the Central Limit Theorem. O D. No, since o is known and the sample size is large enough, the sampling distribution of the mean is approximately normal by the Central Limit Theorem. d. Suppose the standard deviation changes to 99 hours. What are your answers in (a) and (b)? The 95% confidence interval estimate would be from a lower limit of hours to an upper limit of hours. (Round to one decimal place as needed.) Based on the sample data and a standard deviation of 99 hours, the manufacturer V the right to state that the light bulbs have a mean life of 460 hours. A mean of 460 hours is V standard errors the sample mean, so it is V that the light bulbs have mean life of 460 hours
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