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a light bulb manufacture gaurentees that the mean life of a certain type of bulb is at least 875 hours. A random sample of 40 light bulbs has a mean life of 863 hours with a standard deviation of 50. a=0.04
asked by jamie on April 18, 2011 
statistics
1. The new Twinkle bulb has a standard deviation σ = 34 hours. A random sample of 77 light bulbs is selected from inventory. The sample mean was found to be x= 492 hours. Question: Find the margin of error E for a 90% confidence
asked by looking for someone to varify my work please on April 6, 2010 
math
1) A light bulb producing company states that its lights will last an average of 1200 hours with a standard deviation of 200 hours. A sample of 100 light bulbs from the company were tested and the researcher found that the average
asked by Alexus on July 16, 2012 
maths
the life span of an electric bulb is normally distribution with mean 5500 light hours and standard deviation of 1200 light hours . what is the probability that a randomly selected bulb which lasts more than 6000 light hours?
asked by ragul on December 31, 2015 
Business Statistics
The quality control manager at a light bulb factory needs to estimate the mean life of a large shipment of light bulbs. The manufacturer's specifications are that the standard deviations is 100 hours. A random sample of 64 light
asked by Tim on September 20, 2015 
Math
Suppose the number of hours a type of light bulb will burn is normally distributed with a mean 84 with a standard deviation of 9 hours. what is the probability one of these bulbs will burn for more than 90 hours? If a sample of 24
asked by Jess on April 16, 2019 
Statistics
A company has developed a new type of light bulb, and wants to estimate its mean lifetime. A simple random sample of 12 bulbs had a sample mean lifetime of 692 hours with a sample standard deviation of 30 hours. It is reasonable
asked by Sara on July 1, 2013 
Statistics
Can anyone tell me how to use TI84 calculator to solve this problem??? A company has developed a new type of light bulb, and wants to estimate its mean lifetime. A simple random sample of 12 bulbs had a sample mean lifetime of
asked by Anonymous on June 29, 2013 
Statistics
The mean life expectancy of a certain type of light bulb is 945 hours with a standard deviation of 21 hours. What is the approximate standard deviation of the sampling distribution of the mean for all samples with n=50?
asked by tf9346 on May 9, 2016 
Math
A consumer buys n light bulbs, each of which has a lifetime that has a mean of 800 hours, a standard deviation of 100 hours, and a normal distribution. A light bulb is replaced by another as soon as it burns out. Assuming
asked by Alex on April 27, 2011